Proper caching of the contents' volume and weight in the pocket. Many of our systems are not designed to process items in quantity, which means when there are a lot of items ( lets say 4000 or so ) in a pocket, the game can be stuttering when doing certain activities ( opening insert menu, wielding item, etc ). However pockets are often interacted with from high above the call stack thanks to item_location :P. So tracking the contents change is very hard.