diff --git a/src/pretix/base/migrations/0280_cartposition_max_extend.py b/src/pretix/base/migrations/0280_cartposition_max_extend.py
new file mode 100644
index 000000000..16024151f
--- /dev/null
+++ b/src/pretix/base/migrations/0280_cartposition_max_extend.py
@@ -0,0 +1,18 @@
+# Generated by Django 4.2.20 on 2025-05-14 14:58
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('pretixbase', '0279_discount_event_date_from_discount_event_date_until'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='cartposition',
+            name='max_extend',
+            field=models.DateTimeField(null=True),
+        ),
+    ]
diff --git a/src/pretix/base/models/orders.py b/src/pretix/base/models/orders.py
index 7ac8beff1..9db278422 100644
--- a/src/pretix/base/models/orders.py
+++ b/src/pretix/base/models/orders.py
@@ -3098,7 +3098,10 @@ class CartPosition(AbstractPosition):
         verbose_name=_("Expiration date"),
         db_index=True
     )
-
+    max_extend = models.DateTimeField(
+        verbose_name=_("Limit for extending expiration date"),
+        null=True
+    )
     tax_rate = models.DecimalField(
         max_digits=7, decimal_places=2, default=Decimal('0.00'),
         verbose_name=_('Tax rate')
diff --git a/src/pretix/base/services/cart.py b/src/pretix/base/services/cart.py
index d3e359013..14099b8c1 100644
--- a/src/pretix/base/services/cart.py
+++ b/src/pretix/base/services/cart.py
@@ -45,6 +45,7 @@ from django.conf import settings
 from django.core.exceptions import ValidationError
 from django.db import DatabaseError, transaction
 from django.db.models import Count, Exists, IntegerField, OuterRef, Q, Value
+from django.db.models.aggregates import Min
 from django.dispatch import receiver
 from django.utils.timezone import make_aware, now
 from django.utils.translation import (
@@ -275,7 +276,10 @@ class CartManager:
     }
 
     def __init__(self, event: Event, cart_id: str, sales_channel: SalesChannel,
-                 invoice_address: InvoiceAddress=None, widget_data=None, expiry=None):
+                 invoice_address: InvoiceAddress=None, widget_data=None, reservation_time: timedelta=None):
+        """
+        Creates a new CartManager for an event.
+        """
         self.event = event
         self.cart_id = cart_id
         self.real_now_dt = now()
@@ -286,11 +290,17 @@ class CartManager:
         self._subevents_cache = {}
         self._variations_cache = {}
         self._seated_cache = {}
-        self._expiry = None
-        self._explicit_expiry = expiry
         self.invoice_address = invoice_address
         self._widget_data = widget_data or {}
         self._sales_channel = sales_channel
+        self.num_extended_positions = 0
+
+        if reservation_time:
+            self._reservation_time = reservation_time
+        else:
+            self._reservation_time = timedelta(minutes=self.event.settings.get('reservation_time', as_type=int))
+        self._expiry = self.real_now_dt + self._reservation_time
+        self._max_expiry_extend = self.real_now_dt + (self._reservation_time * 11)
 
     @property
     def positions(self):
@@ -305,14 +315,6 @@ class CartManager:
             self._seated_cache[item, subevent] = item.seat_category_mappings.filter(subevent=subevent).exists()
         return self._seated_cache[item, subevent]
 
-    def _calculate_expiry(self):
-        if self._explicit_expiry:
-            self._expiry = self._explicit_expiry
-        else:
-            self._expiry = self.real_now_dt + timedelta(
-                minutes=self.event.settings.get('reservation_time', as_type=int)
-            )
-
     def _check_presale_dates(self):
         if self.event.presale_start and time_machine_now(self.real_now_dt) < self.event.presale_start:
             raise CartError(error_messages['not_started'])
@@ -329,9 +331,27 @@ class CartManager:
                     raise CartError(error_messages['payment_ended'])
 
     def _extend_expiry_of_valid_existing_positions(self):
+        # real_now_dt is initialized at CartManager instantiation, so it's slightly in the past. Add a small
+        # delta to reduce risk of extending already expired CartPositions.
+        padded_now_dt = self.real_now_dt + timedelta(seconds=5)
+
+        # Make sure we do not extend past the max_extend timestamp, allowing users to extend their valid positions up
+        # to 11 times the reservation time. If we add new positions to the cart while valid positions exist, the new
+        # positions' reservation will also be limited to max_extend of the oldest position.
+        # Only after all positions expire, an ExtendOperation may reset max_extend to another 11x reservation_time.
+        max_extend_existing = self.positions.filter(expires__gt=padded_now_dt).aggregate(m=Min('max_extend'))['m']
+        if max_extend_existing:
+            self._expiry = min(self._expiry, max_extend_existing)
+            self._max_expiry_extend = max_extend_existing
+
         # Extend this user's cart session to ensure all items in the cart expire at the same time
         # We can extend the reservation of items which are not yet expired without risk
-        self.positions.filter(expires__gt=self.real_now_dt).update(expires=self._expiry)
+        if self._expiry > padded_now_dt:
+            self.num_extended_positions += self.positions.filter(
+                expires__gt=padded_now_dt, expires__lt=self._expiry,
+            ).update(
+                expires=self._expiry,
+            )
 
     def _delete_out_of_timeframe(self):
         err = None
@@ -1246,6 +1266,7 @@ class CartManager:
                             item=op.item,
                             variation=op.variation,
                             expires=self._expiry,
+                            max_extend=self._max_expiry_extend,
                             cart_id=self.cart_id,
                             voucher=op.voucher,
                             addon_to=op.addon_to if op.addon_to else None,
@@ -1294,7 +1315,9 @@ class CartManager:
                                         event=self.event,
                                         item=b.item,
                                         variation=b.variation,
-                                        expires=self._expiry, cart_id=self.cart_id,
+                                        expires=self._expiry,
+                                        max_extend=self._max_expiry_extend,
+                                        cart_id=self.cart_id,
                                         voucher=None,
                                         addon_to=cp,
                                         subevent=b.subevent,
@@ -1321,12 +1344,14 @@ class CartManager:
                         op.position.delete()
                     elif available_count == 1:
                         op.position.expires = self._expiry
+                        op.position.max_extend = self._max_expiry_extend
                         op.position.listed_price = op.listed_price
                         op.position.price_after_voucher = op.price_after_voucher
                         # op.position.price will be updated by recompute_final_prices_and_taxes()
                         if op.position.pk not in deleted_positions:
                             try:
-                                op.position.save(force_update=True, update_fields=['expires', 'listed_price', 'price_after_voucher'])
+                                op.position.save(force_update=True, update_fields=['expires', 'max_extend', 'listed_price', 'price_after_voucher'])
+                                self.num_extended_positions += 1
                             except DatabaseError:
                                 # Best effort... The position might have been deleted in the meantime!
                                 pass
@@ -1416,14 +1441,11 @@ class CartManager:
     def commit(self):
         self._check_presale_dates()
         self._check_max_cart_size()
-        self._calculate_expiry()
 
         err = self._delete_out_of_timeframe()
         err = self.extend_expired_positions() or err
         err = err or self._check_min_per_voucher()
 
-        self.real_now_dt = now()
-
         self._extend_expiry_of_valid_existing_positions()
         err = self._perform_operations() or err
         self.recompute_final_prices_and_taxes()
@@ -1632,6 +1654,31 @@ def clear_cart(self, event: Event, cart_id: str=None, locale='en', sales_channel
             raise CartError(error_messages['busy'])
 
 
+@app.task(base=ProfiledEventTask, bind=True, max_retries=5, default_retry_delay=1, throws=(CartError,))
+def extend_cart_reservation(self, event: Event, cart_id: str=None, locale='en', sales_channel='web', override_now_dt: datetime=None) -> None:
+    """
+    Resets the expiry time of a cart to the configured reservation time of this event.
+    Limited to 11x the reservation time.
+
+    :param event: The event ID in question
+    :param cart_id: The cart ID of the cart to modify
+    """
+    with language(locale), time_machine_now_assigned(override_now_dt):
+        try:
+            sales_channel = event.organizer.sales_channels.get(identifier=sales_channel)
+        except SalesChannel.DoesNotExist:
+            raise CartError("Invalid sales channel.")
+        try:
+            try:
+                cm = CartManager(event=event, cart_id=cart_id, sales_channel=sales_channel)
+                cm.commit()
+                return cm.num_extended_positions
+            except LockTimeoutException:
+                self.retry()
+        except (MaxRetriesExceededError, LockTimeoutException):
+            raise CartError(error_messages['busy'])
+
+
 @app.task(base=ProfiledEventTask, bind=True, max_retries=5, default_retry_delay=1, throws=(CartError,))
 def set_cart_addons(self, event: Event, addons: List[dict], add_to_cart_items: List[dict], cart_id: str=None, locale='en',
                     invoice_address: int=None, sales_channel='web', override_now_dt: datetime=None) -> None:
diff --git a/src/pretix/presale/templates/pretixpresale/event/fragment_cart.html b/src/pretix/presale/templates/pretixpresale/event/fragment_cart.html
index c9dd89050..02cacd02c 100644
--- a/src/pretix/presale/templates/pretixpresale/event/fragment_cart.html
+++ b/src/pretix/presale/templates/pretixpresale/event/fragment_cart.html
@@ -492,15 +492,21 @@
 <div class="row">
     <div class="col-md-12">
     {% if not cart.is_ordered %}
-        <p class="text-muted" id="cart-deadline" data-expires="{{ cart.first_expiry|date:"Y-m-d H:i:sO" }}">
-            {% if cart.minutes_left > 0 or cart.seconds_left > 0 %}
-                {% blocktrans trimmed with minutes=cart.minutes_left %}
-                    The items in your cart are reserved for you for {{ minutes }} minutes.
-                {% endblocktrans %}
-            {% else %}
-                {% trans "The items in your cart are no longer reserved for you. You can still complete your order as long as they’re available." %}
-            {% endif %}
-        </p>
+        <form class="text-muted"
+                method="post" data-asynctask action="{% eventurl request.event "presale:event.cart.extend" cart_namespace=cart_namespace %}">
+            {% csrf_token %}
+            <span id="cart-deadline" data-expires="{{ cart.first_expiry|date:"Y-m-d H:i:sO" }}">
+                {% if cart.minutes_left > 0 or cart.seconds_left > 0 %}
+                    {% blocktrans trimmed with minutes=cart.minutes_left %}
+                        The items in your cart are reserved for you for {{ minutes }} minutes.
+                    {% endblocktrans %}
+                {% else %}
+                    {% trans "The items in your cart are no longer reserved for you. You can still complete your order as long as they’re available." %}
+                {% endif %}
+            </span>
+            <button class="btn btn-link" type="submit" id="cart-extend-button">
+                <i class="fa fa-refresh" aria-hidden="true"></i> {% trans "Extend" %}</button>
+        </form>
     {% else %}
         <p class="sr-only" id="cart-description">{% trans "Overview of your ordered products." %}</p>
     {% endif %}
diff --git a/src/pretix/presale/urls.py b/src/pretix/presale/urls.py
index 10e8a2f84..e47f5a84e 100644
--- a/src/pretix/presale/urls.py
+++ b/src/pretix/presale/urls.py
@@ -56,6 +56,7 @@ frame_wrapped_urls = [
     re_path(r'^cart/remove$', pretix.presale.views.cart.CartRemove.as_view(), name='event.cart.remove'),
     re_path(r'^cart/voucher$', pretix.presale.views.cart.CartApplyVoucher.as_view(), name='event.cart.voucher'),
     re_path(r'^cart/clear$', pretix.presale.views.cart.CartClear.as_view(), name='event.cart.clear'),
+    re_path(r'^cart/extend$', pretix.presale.views.cart.CartExtendReservation.as_view(), name='event.cart.extend'),
     re_path(r'^cart/answer/(?P<answer>[^/]+)/$',
             pretix.presale.views.cart.AnswerDownload.as_view(),
             name='event.cart.download.answer'),
diff --git a/src/pretix/presale/views/cart.py b/src/pretix/presale/views/cart.py
index a823e6674..f99eac043 100644
--- a/src/pretix/presale/views/cart.py
+++ b/src/pretix/presale/views/cart.py
@@ -62,7 +62,7 @@ from pretix.base.models import (
 )
 from pretix.base.services.cart import (
     CartError, add_items_to_cart, apply_voucher, clear_cart, error_messages,
-    remove_cart_position,
+    extend_cart_reservation, remove_cart_position,
 )
 from pretix.base.timemachine import time_machine_now
 from pretix.base.views.tasks import AsyncAction
@@ -537,6 +537,20 @@ class CartClear(EventViewMixin, CartActionMixin, AsyncAction, View):
                        request.sales_channel.identifier, time_machine_now(default=None))
 
 
+@method_decorator(allow_frame_if_namespaced, 'dispatch')
+class CartExtendReservation(EventViewMixin, CartActionMixin, AsyncAction, View):
+    task = extend_cart_reservation
+    known_errortypes = ['CartError']
+
+    def get_success_message(self, value):
+        if value > 0:
+            return _('Your cart timeout was extended.')
+
+    def post(self, request, *args, **kwargs):
+        return self.do(self.request.event.id, get_or_create_cart_id(self.request), translation.get_language(),
+                       request.sales_channel.identifier, time_machine_now(default=None))
+
+
 @method_decorator(allow_cors_if_namespaced, 'dispatch')
 @method_decorator(allow_frame_if_namespaced, 'dispatch')
 @method_decorator(iframe_entry_view_wrapper, 'dispatch')
diff --git a/src/pretix/static/pretixpresale/js/ui/cart.js b/src/pretix/static/pretixpresale/js/ui/cart.js
index 98a192558..bdb4b14c5 100644
--- a/src/pretix/static/pretixpresale/js/ui/cart.js
+++ b/src/pretix/static/pretixpresale/js/ui/cart.js
@@ -55,6 +55,7 @@ var cart = {
                 pad(diff_minutes.toString(), 2) + ':' + pad(diff_seconds.toString(), 2)
             );
         }
+        $("#cart-extend-button").toggle(diff_minutes < 3);
     },
 
     init: function () {
diff --git a/src/tests/presale/test_cart.py b/src/tests/presale/test_cart.py
index d1d7a901f..da78c4628 100644
--- a/src/tests/presale/test_cart.py
+++ b/src/tests/presale/test_cart.py
@@ -37,6 +37,7 @@ import json
 from datetime import timedelta
 from decimal import Decimal
 
+import freezegun
 from bs4 import BeautifulSoup
 from django.conf import settings
 from django.test import TestCase
@@ -96,6 +97,8 @@ class CartTestMixin:
 
         self.client.get('/%s/%s/' % (self.orga.slug, self.event.slug))
         self.session_key = get_cart_session_key(self.client, self.event)
+        self.event.settings.set('reservation_time', 30)
+        self.cart_reservation_time = timedelta(minutes=self.event.settings.get('reservation_time', as_type=int))
 
 
 class CartTest(CartTestMixin, TestCase):
@@ -989,7 +992,7 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         self.event.settings.max_items_per_order = 5
         response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
@@ -1006,7 +1009,7 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         self.event.settings.max_items_per_order = settings.PRETIX_MAX_ORDER_SIZE + 100
         response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
@@ -1023,7 +1026,7 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         self.event.settings.max_items_per_order = 5
         response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
@@ -1084,7 +1087,7 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
             'item_%d' % self.ticket.id: '2',
@@ -1102,7 +1105,7 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
             'item_%d' % self.ticket.id: '2',
@@ -1225,22 +1228,102 @@ class CartTest(CartTestMixin, TestCase):
         self.assertEqual(objs[0].price, 23)
 
     def test_renew_in_time(self):
+        start_time = now() - timedelta(minutes=20)
+        expires = start_time + self.cart_reservation_time
+        max_extend = start_time + 11 * self.cart_reservation_time
         with scopes_disabled():
             cp = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=expires, max_extend=max_extend
             )
         self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
             'variation_%d_%d' % (self.shirt.id, self.shirt_red.id): '1'
         }, follow=True)
         cp.refresh_from_db()
         self.assertGreater(cp.expires, now() + timedelta(minutes=10))
+        self.assertEqual(cp.max_extend, max_extend)
+
+    def test_autorenew_with_max_extend(self):
+        start_time = datetime.datetime(2024, 1, 1, 10, 00, 00, tzinfo=datetime.timezone.utc)
+        with freezegun.freeze_time(start_time):
+            expires = start_time + self.cart_reservation_time
+            max_extend = start_time + 2 * self.cart_reservation_time
+            with scopes_disabled():
+                cp = CartPosition.objects.create(
+                    event=self.event, cart_id=self.session_key, item=self.ticket,
+                    price=23, expires=expires, max_extend=max_extend
+                )
+        with freezegun.freeze_time(start_time + timedelta(minutes=20)):
+            self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
+                'item_%d' % (self.ticket.id,): '1'
+            }, follow=True)
+            cp.refresh_from_db()
+            with scopes_disabled():
+                positions = list(CartPosition.objects.filter(cart_id=cp.cart_id))
+            self.assertEqual(len(positions), 2)
+            for pos in positions:
+                self.assertEqual(pos.expires, start_time + timedelta(minutes=20) + self.cart_reservation_time)
+                self.assertEqual(pos.max_extend, max_extend)
+        with freezegun.freeze_time(start_time + timedelta(minutes=45)):
+            self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
+                'item_%d' % (self.ticket.id,): '1'
+            }, follow=True)
+            cp.refresh_from_db()
+            with scopes_disabled():
+                positions = list(CartPosition.objects.filter(cart_id=cp.cart_id))
+            self.assertEqual(len(positions), 3)
+            for pos in positions:
+                self.assertEqual(pos.expires, max_extend)
+                self.assertEqual(pos.max_extend, max_extend)
+        with freezegun.freeze_time(start_time + timedelta(days=1)):
+            self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
+                'item_%d' % (self.ticket.id,): '1'
+            }, follow=True)
+            cp.refresh_from_db()
+            with scopes_disabled():
+                positions = list(CartPosition.objects.filter(cart_id=cp.cart_id))
+            self.assertEqual(len(positions), 4)
+            for pos in positions:
+                self.assertEqual(pos.expires, start_time + timedelta(days=1) + self.cart_reservation_time)
+                self.assertEqual(pos.max_extend, start_time + timedelta(days=1) + 11 * self.cart_reservation_time)
+
+    def test_extend_with_max_extend(self):
+        start_time = datetime.datetime(2024, 1, 1, 10, 00, 00, tzinfo=datetime.timezone.utc)
+        with freezegun.freeze_time(start_time):
+            expires = start_time + self.cart_reservation_time
+            max_extend = start_time + 2 * self.cart_reservation_time
+            with scopes_disabled():
+                cp = CartPosition.objects.create(
+                    event=self.event, cart_id=self.session_key, item=self.ticket,
+                    price=23, expires=expires, max_extend=max_extend
+                )
+        with freezegun.freeze_time(start_time + timedelta(minutes=20)):
+            self.client.post('/%s/%s/cart/extend' % (self.orga.slug, self.event.slug), {
+            }, follow=True)
+            cp.refresh_from_db()
+            self.assertEqual(cp.expires, start_time + timedelta(minutes=20) + self.cart_reservation_time)
+            self.assertEqual(cp.max_extend, max_extend)
+        with freezegun.freeze_time(start_time + timedelta(minutes=45)):
+            self.client.post('/%s/%s/cart/extend' % (self.orga.slug, self.event.slug), {
+            }, follow=True)
+            cp.refresh_from_db()
+            self.assertEqual(cp.expires, max_extend)
+            self.assertEqual(cp.max_extend, max_extend)
+        with freezegun.freeze_time(start_time + timedelta(minutes=65)):
+            self.client.post('/%s/%s/cart/extend' % (self.orga.slug, self.event.slug), {
+            }, follow=True)
+            cp.refresh_from_db()
+            self.assertEqual(cp.expires, start_time + timedelta(minutes=65) + self.cart_reservation_time)
+            self.assertEqual(cp.max_extend, start_time + timedelta(minutes=65) + 11 * self.cart_reservation_time)
 
     def test_renew_expired_successfully(self):
+        start_time = now() - timedelta(minutes=40)
+        expires = start_time + self.cart_reservation_time
+        max_extend = start_time + 11 * self.cart_reservation_time
         with scopes_disabled():
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() - timedelta(minutes=10)
+                price=23, expires=expires, max_extend=max_extend
             )
         self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
             'variation_%d_%d' % (self.shirt.id, self.shirt_red.id): '1'
@@ -1250,13 +1333,14 @@ class CartTest(CartTestMixin, TestCase):
         self.assertEqual(obj.item, self.ticket)
         self.assertIsNone(obj.variation)
         self.assertEqual(obj.price, 23)
-        self.assertGreater(obj.expires, now())
+        self.assertGreater(obj.expires, now() + timedelta(minutes=10))
+        self.assertGreater(obj.max_extend, now() + 11 * self.cart_reservation_time - timedelta(minutes=10))
 
     def test_renew_questions(self):
         with scopes_disabled():
             cr1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() - timedelta(minutes=10)
+                price=23, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             q1 = Question.objects.create(
                 event=self.event, question='Age', type=Question.TYPE_NUMBER,
@@ -1279,7 +1363,7 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() - timedelta(minutes=10)
+                price=23, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
             'item_%d' % self.ticket.id: '1',
@@ -1289,6 +1373,61 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             self.assertFalse(CartPosition.objects.filter(id=cp1.id).exists())
 
+    def test_expired_renew_fails_partially_and_add_succeeds(self):
+        start_time = datetime.datetime(2024, 1, 1, 10, 00, 00, tzinfo=datetime.timezone.utc)
+        expires = start_time + self.cart_reservation_time
+        max_extend = start_time + 11 * self.cart_reservation_time
+        self.quota_tickets.size = 0
+        self.quota_tickets.save()
+        with scopes_disabled():
+            cp1 = CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.ticket,
+                price=23, expires=expires, max_extend=max_extend
+            )
+            cp2 = CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_blue,
+                price=23, expires=expires, max_extend=max_extend
+            )
+        with freezegun.freeze_time(max_extend + timedelta(hours=1)):
+            response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
+                'variation_%d_%d' % (self.shirt.id, self.shirt_red.id): '1',
+            }, follow=True)
+            doc = BeautifulSoup(response.rendered_content, "lxml")
+            self.assertIn('no longer available', doc.select('.alert-danger')[0].text)
+            with scopes_disabled():
+                self.assertFalse(CartPosition.objects.filter(id=cp1.id).exists())
+                cp2.refresh_from_db()
+                self.assertEqual(cp2.expires, now() + self.cart_reservation_time)
+                self.assertEqual(cp2.max_extend, now() + 11 * self.cart_reservation_time)
+                cp3 = CartPosition.objects.get(variation_id=self.shirt_red.id)
+                self.assertEqual(cp3.expires, now() + self.cart_reservation_time)
+                self.assertEqual(cp3.max_extend, now() + 11 * self.cart_reservation_time)
+
+    def test_expired_cart_extend_fails_partially(self):
+        start_time = datetime.datetime(2024, 1, 1, 10, 00, 00, tzinfo=datetime.timezone.utc)
+        max_extend = start_time + 11 * self.cart_reservation_time
+        self.quota_tickets.size = 0
+        self.quota_tickets.save()
+        with scopes_disabled():
+            cp1 = CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.ticket,
+                price=23, expires=max_extend, max_extend=max_extend
+            )
+            cp2 = CartPosition.objects.create(
+                event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_blue,
+                price=23, expires=max_extend, max_extend=max_extend
+            )
+        with freezegun.freeze_time(max_extend + timedelta(hours=1)):
+            response = self.client.post('/%s/%s/cart/extend' % (self.orga.slug, self.event.slug), {
+            }, follow=True)
+            doc = BeautifulSoup(response.rendered_content, "lxml")
+            self.assertIn('no longer available', doc.select('.alert-danger')[0].text)
+            with scopes_disabled():
+                self.assertFalse(CartPosition.objects.filter(id=cp1.id).exists())
+                cp2.refresh_from_db()
+                self.assertEqual(cp2.expires, now() + self.cart_reservation_time)
+                self.assertEqual(cp2.max_extend, now() + 11 * self.cart_reservation_time)
+
     def test_subevent_renew_expired_successfully(self):
         self.event.has_subevents = True
         self.event.save()
@@ -1300,7 +1439,9 @@ class CartTest(CartTestMixin, TestCase):
             self.quota_shirts.save()
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() - timedelta(minutes=10), subevent=se
+                price=23,
+                expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+                subevent=se
             )
         self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
             'variation_%d_%d' % (self.shirt.id, self.shirt_red.id): '1',
@@ -1324,7 +1465,9 @@ class CartTest(CartTestMixin, TestCase):
             self.quota_tickets.save()
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() - timedelta(minutes=10), subevent=se
+                price=23,
+                expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+                subevent=se
             )
         response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
             'item_%d' % self.ticket.id: '1',
@@ -1339,7 +1482,7 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         response = self.client.post('/%s/%s/cart/remove' % (self.orga.slug, self.event.slug), {
             'id': cp.pk
@@ -1355,15 +1498,15 @@ class CartTest(CartTestMixin, TestCase):
                                        redeemed=1, min_usages=3, max_usages=10)
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket, voucher=v,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             cp2 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket, voucher=v,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             cp3 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket, voucher=v,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         self.client.post('/%s/%s/cart/remove' % (self.orga.slug, self.event.slug), {
             'id': cp3.pk
@@ -1384,11 +1527,11 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             cp = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         response = self.client.post('/%s/%s/cart/remove' % (self.orga.slug, self.event.slug), {
             'id': cp.pk
@@ -1402,7 +1545,7 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_red,
-                price=14, expires=now() + timedelta(minutes=10)
+                price=14, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         response = self.client.post('/%s/%s/cart/remove' % (self.orga.slug, self.event.slug), {
             'id': cp.pk
@@ -1416,7 +1559,7 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp = CartPosition.objects.create(
                 event=self.event, cart_id='invalid', item=self.shirt, variation=self.shirt_red,
-                price=14, expires=now() + timedelta(minutes=10)
+                price=14, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         response = self.client.post('/%s/%s/cart/remove' % (self.orga.slug, self.event.slug), {
             'id': cp.pk
@@ -1428,11 +1571,11 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         response = self.client.post('/%s/%s/cart/remove' % (self.orga.slug, self.event.slug), {
             'id': cp.pk
@@ -1446,15 +1589,15 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() + timedelta(minutes=10)
+                price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_red,
-                price=14, expires=now() + timedelta(minutes=10)
+                price=14, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         response = self.client.post('/%s/%s/cart/clear' % (self.orga.slug, self.event.slug), {}, follow=True)
         doc = BeautifulSoup(response.rendered_content, "lxml")
@@ -1467,7 +1610,8 @@ class CartTest(CartTestMixin, TestCase):
             v = Voucher.objects.create(item=self.ticket, event=self.event, valid_until=now() - timedelta(days=1))
             cp = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() - timedelta(minutes=10), voucher=v
+                price=23, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+                voucher=v
             )
         self.client.post('/%s/%s/cart/remove' % (self.orga.slug, self.event.slug), {
             'id': cp.pk
@@ -1495,7 +1639,8 @@ class CartTest(CartTestMixin, TestCase):
             v = Voucher.objects.create(item=self.ticket, event=self.event, block_quota=True)
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, expires=now() - timedelta(minutes=10), voucher=v
+                price=23, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+                voucher=v
             )
         self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
             'variation_%d_%d' % (self.shirt.id, self.shirt_red.id): '1',
@@ -2110,7 +2255,8 @@ class CartTest(CartTestMixin, TestCase):
             v = Voucher.objects.create(item=self.ticket, value=Decimal('12.00'), event=self.event,
                                        max_usages=2, redeemed=1)
             CartPosition.objects.create(
-                expires=now() - timedelta(minutes=10), item=self.ticket, voucher=v, price=Decimal('12.00'),
+                expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+                item=self.ticket, voucher=v, price=Decimal('12.00'),
                 event=self.event, cart_id=self.session_key
             )
         response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
@@ -2128,7 +2274,8 @@ class CartTest(CartTestMixin, TestCase):
             v = Voucher.objects.create(item=self.ticket, value=Decimal('12.00'), event=self.event,
                                        max_usages=2, redeemed=1)
             CartPosition.objects.create(
-                expires=now() + timedelta(minutes=10), item=self.ticket, voucher=v, price=Decimal('12.00'),
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+                item=self.ticket, voucher=v, price=Decimal('12.00'),
                 event=self.event, cart_id='other'
             )
         response = self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
@@ -2146,7 +2293,8 @@ class CartTest(CartTestMixin, TestCase):
             v = Voucher.objects.create(item=self.ticket, value=Decimal('12.00'), event=self.event,
                                        max_usages=2, redeemed=1)
             CartPosition.objects.create(
-                expires=now() - timedelta(minutes=10), item=self.ticket, voucher=v, price=Decimal('12.00'),
+                expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+                item=self.ticket, voucher=v, price=Decimal('12.00'),
                 event=self.event, cart_id='other'
             )
         self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
@@ -2161,11 +2309,13 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, listed_price=23, price_after_voucher=23, expires=now() + timedelta(minutes=10)
+                price=23, listed_price=23, price_after_voucher=23,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             cp2 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_blue,
-                price=15, listed_price=15, price_after_voucher=15, expires=now() + timedelta(minutes=10)
+                price=15, listed_price=15, price_after_voucher=15,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             v = Voucher.objects.create(
                 event=self.event, item=self.ticket, price_mode='set', value=Decimal('4.00')
@@ -2185,11 +2335,13 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, listed_price=23, price_after_voucher=23, expires=now() + timedelta(minutes=10)
+                price=23, listed_price=23, price_after_voucher=23,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             cp2 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_blue,
-                price=150, listed_price=150, price_after_voucher=150, expires=now() + timedelta(minutes=10)
+                price=150, listed_price=150, price_after_voucher=150,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             v = Voucher.objects.create(
                 event=self.event, price_mode='set', value=Decimal('4.00'), max_usages=100, redeemed=99
@@ -2210,11 +2362,13 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, listed_price=23, price_after_voucher=23, expires=now() + timedelta(minutes=10)
+                price=23, listed_price=23, price_after_voucher=23,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             cp2 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_blue,
-                price=150, listed_price=150, price_after_voucher=150, expires=now() + timedelta(minutes=10)
+                price=150, listed_price=150, price_after_voucher=150,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             v = Voucher.objects.create(
                 event=self.event, price_mode='set', quota=self.quota_all, value=Decimal('4.00'), max_usages=100
@@ -2235,11 +2389,13 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, listed_price=23, price_after_voucher=23, expires=now() + timedelta(minutes=10)
+                price=23, listed_price=23, price_after_voucher=23,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             cp2 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_blue,
-                price=150, listed_price=150, price_after_voucher=150, expires=now() + timedelta(minutes=10)
+                price=150, listed_price=150, price_after_voucher=150,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             v = Voucher.objects.create(
                 event=self.event, price_mode='set', quota=self.quota_all, value=Decimal('4.00'), max_usages=100,
@@ -2274,14 +2430,17 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, listed_price=23, price_after_voucher=23, expires=now() + timedelta(minutes=10)
+                price=23, listed_price=23, price_after_voucher=23,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             v2 = Voucher.objects.create(
                 event=self.event, price_mode='set', quota=self.quota_all, value=Decimal('8.00'), max_usages=100
             )
             cp2 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_blue,
-                price=8, expires=now() + timedelta(minutes=10), voucher=v2
+                price=8,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+                voucher=v2
             )
             v = Voucher.objects.create(
                 event=self.event, price_mode='set', quota=self.quota_all, value=Decimal('4.00'), max_usages=100
@@ -2327,11 +2486,13 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, listed_price=23, price_after_voucher=23, expires=now() + timedelta(minutes=10)
+                price=23, listed_price=23, price_after_voucher=23,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             cp2 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_blue,
-                price=15, listed_price=15, price_after_voucher=15, expires=now() + timedelta(minutes=10)
+                price=15, listed_price=15, price_after_voucher=15,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             v = Voucher.objects.create(
                 event=self.event, price_mode='set', value=Decimal('40.00'), max_usages=100,
@@ -2351,11 +2512,13 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp1 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, listed_price=23, price_after_voucher=23, expires=now() + timedelta(minutes=10)
+                price=23, listed_price=23, price_after_voucher=23,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             cp2 = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_blue,
-                price=15, listed_price=15, price_after_voucher=15, expires=now() + timedelta(minutes=10)
+                price=15, listed_price=15, price_after_voucher=15,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             v = Voucher.objects.create(
                 event=self.event, price_mode='set', value=Decimal('40.00'), max_usages=100, redeemed=100
@@ -2374,11 +2537,12 @@ class CartTest(CartTestMixin, TestCase):
         with scopes_disabled():
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket,
-                price=23, listed_price=23, price_after_voucher=23, expires=now() + timedelta(minutes=10)
+                price=23, listed_price=23, price_after_voucher=23,
+                expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.shirt, variation=self.shirt_blue,
-                price=8, expires=now() + timedelta(minutes=10),
+                price=8, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
             )
             gc = self.orga.issued_gift_cards.create(secret="GIFTCARD", currency=self.event.currency)
             gc.transactions.create(value=Decimal("12.24"), acceptor=self.orga)
@@ -2491,7 +2655,8 @@ class CartAddonTest(CartTestMixin, TestCase):
         self.addon1.price_included = True
         self.addon1.save()
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
 
@@ -2512,11 +2677,13 @@ class CartAddonTest(CartTestMixin, TestCase):
         self.addon1.price_included = True
         self.addon1.save()
         cp1 = CartPosition.objects.create(
-            expires=now() - timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         cp2 = CartPosition.objects.create(
-            expires=now() - timedelta(minutes=10), item=self.workshop1, price=Decimal('0.00'),
+            expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.workshop1, price=Decimal('0.00'),
             event=self.event, cart_id=self.session_key, addon_to=cp1
         )
         self.cm.extend_expired_positions()
@@ -2533,11 +2700,13 @@ class CartAddonTest(CartTestMixin, TestCase):
         self.quota_tickets.size = 0
         self.quota_tickets.save()
         cp1 = CartPosition.objects.create(
-            expires=now() - timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         CartPosition.objects.create(
-            expires=now() - timedelta(minutes=10), item=self.workshop1, price=Decimal('0.00'),
+            expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.workshop1, price=Decimal('0.00'),
             event=self.event, cart_id=self.session_key, addon_to=cp1
         )
         self.cm.extend_expired_positions()
@@ -2550,7 +2719,8 @@ class CartAddonTest(CartTestMixin, TestCase):
         self.addon1.price_included = True
         self.addon1.save()
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
 
@@ -2575,7 +2745,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_cart_set_simple_addon(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
 
@@ -2599,7 +2770,8 @@ class CartAddonTest(CartTestMixin, TestCase):
         self.workshopquota.subevent = se
         self.workshopquota.save()
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key, subevent=se
         )
 
@@ -2625,7 +2797,8 @@ class CartAddonTest(CartTestMixin, TestCase):
         self.workshopquota.subevent = se2
         self.workshopquota.save()
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key, subevent=se
         )
 
@@ -2641,7 +2814,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_wrong_category(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         self.workshop1.category = self.category
@@ -2658,7 +2832,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_invalid_parent(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id='other'
         )
         with self.assertRaises(CartError):
@@ -2674,7 +2849,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     def test_no_quota_for_addon(self):
         self.workshopquota.delete()
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         with self.assertRaises(CartError):
@@ -2689,7 +2865,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_unknown_addon_item(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         with self.assertRaises(CartError):
@@ -2704,11 +2881,13 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_duplicate_items_for_other_cp(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         cp2 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         self.cm.set_addons([
@@ -2730,7 +2909,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_multi_allowed(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         self.addon1.max_count = 2
@@ -2754,7 +2934,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_number_exceeds_max(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         self.addon1.max_count = 2
@@ -2777,7 +2958,8 @@ class CartAddonTest(CartTestMixin, TestCase):
         self.workshopquota.size = 1
         self.workshopquota.save()
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         self.addon1.max_count = 2
@@ -2800,7 +2982,8 @@ class CartAddonTest(CartTestMixin, TestCase):
         self.workshop3.free_price = True
         self.workshop3.save()
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         self.addon1.max_count = 5
@@ -2838,7 +3021,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_change_number(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         self.addon1.max_count = 5
@@ -2882,7 +3066,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_no_duplicate_items_for_same_cp(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         self.addon1.max_count = 2
@@ -2917,7 +3102,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_addon_max_count(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         with self.assertRaises(CartError):
@@ -2952,7 +3138,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_addon_min_count(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         self.addon1.min_count = 2
@@ -2983,11 +3170,13 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_remove_with_addons(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         cp2 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.workshop1, price=Decimal('12.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.workshop1, price=Decimal('12.00'),
             event=self.event, cart_id=self.session_key, addon_to=cp1
         )
         self.cm.remove_item(cp1.pk)
@@ -2998,11 +3187,13 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_remove_addons(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         cp2 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.workshop1, price=Decimal('12.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.workshop1, price=Decimal('12.00'),
             event=self.event, cart_id=self.session_key, addon_to=cp1
         )
         self.cm.set_addons([])
@@ -3012,11 +3203,13 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_remove_addons_below_min(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         cp2 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.workshop1, price=Decimal('12.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.workshop1, price=Decimal('12.00'),
             event=self.event, cart_id=self.session_key, addon_to=cp1
         )
         self.addon1.min_count = 1
@@ -3029,11 +3222,13 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_change_product(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.workshop1, price=Decimal('12.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.workshop1, price=Decimal('12.00'),
             event=self.event, cart_id=self.session_key, addon_to=cp1
         )
         self.cm.set_addons([
@@ -3051,11 +3246,13 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_unchanged(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.workshop1, price=Decimal('12.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.workshop1, price=Decimal('12.00'),
             event=self.event, cart_id=self.session_key, addon_to=cp1
         )
         self.cm.set_addons([
@@ -3071,7 +3268,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     def test_exceed_max(self):
         self.event.settings.max_items_per_order = 1
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         self.cm.set_addons([
@@ -3086,7 +3284,8 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_sold_out(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         self.workshopquota.size = 0
@@ -3104,11 +3303,13 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_sold_out_unchanged(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.workshop1, price=Decimal('12.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.workshop1, price=Decimal('12.00'),
             event=self.event, cart_id=self.session_key, addon_to=cp1
         )
         self.workshopquota.size = 0
@@ -3125,19 +3326,23 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_sold_out_swap_addons(self):
         cp1 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.workshop1, price=Decimal('12.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.workshop1, price=Decimal('12.00'),
             event=self.event, cart_id=self.session_key, addon_to=cp1
         )
         cp2 = CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         CartPosition.objects.create(
-            expires=now() + timedelta(minutes=10), item=self.workshop2, price=Decimal('12.00'),
+            expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.workshop2, price=Decimal('12.00'),
             event=self.event, cart_id=self.session_key, addon_to=cp2
         )
         self.workshopquota.size = 0
@@ -3163,11 +3368,13 @@ class CartAddonTest(CartTestMixin, TestCase):
     @classscope(attr='orga')
     def test_expand_expired(self):
         cp1 = CartPosition.objects.create(
-            expires=now() - timedelta(minutes=10), item=self.ticket, price=Decimal('23.00'),
+            expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('23.00'),
             event=self.event, cart_id=self.session_key
         )
         cp2 = CartPosition.objects.create(
-            expires=now() - timedelta(minutes=10), item=self.workshop1, price=Decimal('12.00'),
+            expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.workshop1, price=Decimal('12.00'),
             event=self.event, cart_id=self.session_key, addon_to=cp1
         )
         self.cm.extend_expired_positions()
@@ -3183,7 +3390,8 @@ class CartAddonTest(CartTestMixin, TestCase):
         v = Voucher.objects.create(item=self.ticket, value=Decimal('20.00'), event=self.event, price_mode='set',
                                    valid_until=now() + timedelta(days=2), max_usages=999, redeemed=0)
         cp1 = CartPosition.objects.create(
-            expires=now() - timedelta(minutes=10), item=self.ticket, price=Decimal('21.50'),
+            expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            item=self.ticket, price=Decimal('21.50'),
             event=self.event, cart_id=self.session_key, voucher=v
         )
         self.cm.extend_expired_positions()
@@ -3647,11 +3855,12 @@ class CartBundleTest(CartTestMixin, TestCase):
     def test_extend_keep_price(self):
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() - timedelta(minutes=10)
+            price=21.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         b = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() - timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         self.cm.commit()
         cp.refresh_from_db()
@@ -3663,11 +3872,12 @@ class CartBundleTest(CartTestMixin, TestCase):
     def test_extend_designated_price_changed(self):
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() - timedelta(minutes=10)
+            price=21.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         b = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() - timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         self.bundle1.designated_price = Decimal('2.00')
         self.bundle1.save()
@@ -3681,11 +3891,12 @@ class CartBundleTest(CartTestMixin, TestCase):
     def test_extend_designated_price_changed_beyond_base_price(self):
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() - timedelta(minutes=10)
+            price=21.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         b = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() - timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         self.bundle1.designated_price = Decimal('40.00')
         self.bundle1.save()
@@ -3699,11 +3910,12 @@ class CartBundleTest(CartTestMixin, TestCase):
     def test_voucher_apply_multiple(self):
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() + timedelta(minutes=10)
+            price=21.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         b = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() + timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         v = Voucher.objects.create(
             event=self.event, price_mode='set', value=Decimal('4.00'), max_usages=100
@@ -3720,11 +3932,12 @@ class CartBundleTest(CartTestMixin, TestCase):
     def test_voucher_apply_multiple_reduce_beyond_designated_price(self):
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() + timedelta(minutes=10)
+            price=21.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         b = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() + timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         v = Voucher.objects.create(
             event=self.event, price_mode='set', value=Decimal('0.00'), max_usages=100
@@ -3745,11 +3958,12 @@ class CartBundleTest(CartTestMixin, TestCase):
         self.trans.save()
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() + timedelta(minutes=10)
+            price=21.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         b = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() + timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         v = Voucher.objects.create(
             event=self.event, price_mode='set', value=Decimal('0.00'), max_usages=100
@@ -3766,15 +3980,17 @@ class CartBundleTest(CartTestMixin, TestCase):
     def test_voucher_apply_affect_bundled(self):
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() + timedelta(minutes=10)
+            price=21.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         a = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=2.5, expires=now() + timedelta(minutes=10), is_bundled=False
+            price=2.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=False
         )
         b = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() + timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         v = Voucher.objects.create(
             event=self.event, price_mode='set', value=Decimal('0.00'), max_usages=100,
@@ -3794,15 +4010,17 @@ class CartBundleTest(CartTestMixin, TestCase):
     def test_voucher_apply_affect_addons(self):
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() + timedelta(minutes=10)
+            price=21.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         a = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() + timedelta(minutes=10), is_bundled=False
+            price=1.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=False
         )
         b = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() + timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         v = Voucher.objects.create(
             event=self.event, price_mode='set', value=Decimal('0.00'), max_usages=100,
@@ -3822,11 +4040,12 @@ class CartBundleTest(CartTestMixin, TestCase):
     def test_extend_base_price_changed(self):
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() - timedelta(minutes=10)
+            price=21.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         b = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() - timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         self.ticket.default_price = Decimal('25.00')
         self.ticket.save()
@@ -3840,15 +4059,17 @@ class CartBundleTest(CartTestMixin, TestCase):
     def test_extend_bundled_and_addon(self):
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() - timedelta(minutes=10)
+            price=21.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         a = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() - timedelta(minutes=10), is_bundled=False
+            price=1.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=False
         )
         b = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() - timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         self.cm.commit()
         cp.refresh_from_db()
@@ -3873,11 +4094,12 @@ class CartBundleTest(CartTestMixin, TestCase):
 
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() - timedelta(minutes=10)
+            price=21.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         a = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() - timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         self.cm.invoice_address = ia
         self.cm.recompute_final_prices_and_taxes()
@@ -3913,11 +4135,12 @@ class CartBundleTest(CartTestMixin, TestCase):
 
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() - timedelta(minutes=10)
+            price=21.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         a = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.5, expires=now() - timedelta(minutes=10), is_bundled=True
+            price=1.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True
         )
         self.cm.invoice_address = ia
         self.cm.recompute_final_prices_and_taxes()
@@ -4048,11 +4271,12 @@ class CartBundleTest(CartTestMixin, TestCase):
 
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.5, expires=now() - timedelta(minutes=10),
+            price=21.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
         )
         a = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.47, expires=now() - timedelta(minutes=10), is_bundled=True, tax_rate=Decimal('5.00')
+            price=1.47, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True, tax_rate=Decimal('5.00')
         )
         self.cm.invoice_address = ia
         self.cm.recompute_final_prices_and_taxes()
@@ -4097,11 +4321,12 @@ class CartBundleTest(CartTestMixin, TestCase):
 
         cp = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket,
-            price=21.68, expires=now() - timedelta(minutes=10), tax_rate=Decimal('20.00')
+            price=21.68, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time, tax_rate=Decimal('20.00')
         )
         a = CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.trans, addon_to=cp,
-            price=1.47, expires=now() - timedelta(minutes=10), is_bundled=True, tax_rate=Decimal('5.00')
+            price=1.47, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time,
+            is_bundled=True, tax_rate=Decimal('5.00')
         )
         self.cm.invoice_address = ia
         self.cm.recompute_final_prices_and_taxes()
@@ -4342,7 +4567,7 @@ class CartSeatingTest(CartTestMixin, TestCase):
     def test_add_with_seat_to_cart_twice(self):
         CartPosition.objects.create(
             event=self.event, cart_id=self.session_key, item=self.ticket, seat=self.seat_a1,
-            price=23, expires=now() + timedelta(minutes=10)
+            price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         with scopes_disabled():
             objs = list(CartPosition.objects.filter(cart_id=self.session_key, event=self.event))
@@ -4358,7 +4583,7 @@ class CartSeatingTest(CartTestMixin, TestCase):
     def test_add_used_seat_to_cart(self):
         CartPosition.objects.create(
             event=self.event, cart_id='aaa', item=self.ticket, seat=self.seat_a1,
-            price=23, expires=now() + timedelta(minutes=10)
+            price=23, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
         )
         self.client.post('/%s/%s/cart/add' % (self.orga.slug, self.event.slug), {
             'seat_%d' % self.ticket.id: self.seat_a1.seat_guid,
@@ -4372,7 +4597,7 @@ class CartSeatingTest(CartTestMixin, TestCase):
         with scopes_disabled():
             cp = CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket, seat=self.seat_a1,
-                price=21.5, expires=now() - timedelta(minutes=10)
+                price=21.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         self.cm.commit()
         cp.refresh_from_db()
@@ -4383,11 +4608,11 @@ class CartSeatingTest(CartTestMixin, TestCase):
         with scopes_disabled():
             CartPosition.objects.create(
                 event=self.event, cart_id=self.session_key, item=self.ticket, seat=self.seat_a1,
-                price=21.5, expires=now() - timedelta(minutes=10)
+                price=21.5, expires=now() - timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
             CartPosition.objects.create(
                 event=self.event, cart_id='secondcart', item=self.ticket, seat=self.seat_a1,
-                price=21.5, expires=now() + timedelta(minutes=10)
+                price=21.5, expires=now() + timedelta(minutes=10), max_extend=now() + 10 * self.cart_reservation_time
             )
         with self.assertRaises(CartError):
             self.cm.commit()