diff --git a/cms/envs/common.py b/cms/envs/common.py
index 8f974e73e5..9fd61ec8c7 100644
--- a/cms/envs/common.py
+++ b/cms/envs/common.py
@@ -2193,7 +2193,7 @@ CACHES = {
         'KEY_PREFIX': 'course_structure',
         'KEY_FUNCTION': 'common.djangoapps.util.memcache.safe_key',
         'LOCATION': ['localhost:11211'],
-        'TIMEOUT': '7200',
+        'TIMEOUT': '604800',  # 1 week
         'BACKEND': 'django.core.cache.backends.memcached.PyMemcacheCache',
         'OPTIONS': {
             'no_delay': True,
diff --git a/cms/envs/devstack-experimental.yml b/cms/envs/devstack-experimental.yml
index 54f6edf8f9..c08b19045f 100644
--- a/cms/envs/devstack-experimental.yml
+++ b/cms/envs/devstack-experimental.yml
@@ -84,7 +84,7 @@ CACHES:
         KEY_PREFIX: course_structure
         LOCATION:
         - edx.devstack.memcached:11211
-        TIMEOUT: '7200'
+        TIMEOUT: '604800'
     default:
         BACKEND: django.core.cache.backends.memcached.PyMemcacheCache
         OPTIONS:
diff --git a/lms/envs/common.py b/lms/envs/common.py
index 1b305f0059..bf11453e98 100644
--- a/lms/envs/common.py
+++ b/lms/envs/common.py
@@ -1148,7 +1148,7 @@ CACHES = {
         'KEY_PREFIX': 'course_structure',
         'KEY_FUNCTION': 'common.djangoapps.util.memcache.safe_key',
         'LOCATION': ['localhost:11211'],
-        'TIMEOUT': '7200',
+        'TIMEOUT': '604800',  # 1 week
         'BACKEND': 'django.core.cache.backends.memcached.PyMemcacheCache',
         'OPTIONS': {
             'no_delay': True,
diff --git a/lms/envs/devstack-experimental.yml b/lms/envs/devstack-experimental.yml
index 63812686e8..149cf09821 100644
--- a/lms/envs/devstack-experimental.yml
+++ b/lms/envs/devstack-experimental.yml
@@ -102,7 +102,7 @@ CACHES:
         KEY_PREFIX: course_structure
         LOCATION:
         - edx.devstack.memcached:11211
-        TIMEOUT: '7200'
+        TIMEOUT: '604800'
     default:
         BACKEND: django.core.cache.backends.memcached.PyMemcacheCache
         OPTIONS:
diff --git a/xmodule/modulestore/split_mongo/mongo_connection.py b/xmodule/modulestore/split_mongo/mongo_connection.py
index 277aff28d4..964bb238c6 100644
--- a/xmodule/modulestore/split_mongo/mongo_connection.py
+++ b/xmodule/modulestore/split_mongo/mongo_connection.py
@@ -246,9 +246,10 @@ class CourseStructureCache:
             data_size = len(compressed_pickled_data)
             tagger.measure('compressed_size', data_size)
 
-            # Structures are immutable, so we set a timeout of "never"
+            # We rely on the course structure cache default timeout, which should be
+            # high by default (~ a few days).
             try:
-                self.cache.set(key, compressed_pickled_data, None)
+                self.cache.set(key, compressed_pickled_data)
             except Exception:  # pylint: disable=broad-except
                 total_bytes_in_one_mb = 1024 * 1024
                 chunk_size_in_mbs = round(data_size / total_bytes_in_one_mb, 2)