diff --git a/boards/models/user.py b/boards/models/user.py
--- a/boards/models/user.py
+++ b/boards/models/user.py
@@ -56,8 +56,8 @@ class User(models.Model):
         tags = self.fav_tags.annotate(Count('threads')) \
             .filter(threads__count__gt=0).order_by('name')
 
-        if tags.exists():
-            cache.set(cache_key, tags, settings.CACHE_TIMEOUT)
+        if tags:
+            cache.set(cache_key, tags)
 
         return tags
 
@@ -68,8 +68,12 @@ class User(models.Model):
         return self.user_id + '(' + str(self.rank) + ')'
 
     def get_last_access_time(self):
+        """
+        Gets user's last post time.
+        """
+
         posts = Post.objects.filter(user=self)
-        if posts.count() > 0:
+        if posts.exists() > 0:
             return posts.latest('pub_time').pub_time
 
     def add_tag(self, tag):