The ability to have a list of items that need to be purchased again when they "run out" (milk, body wash, etc). So I add the item to a shopping list when I need it and when I run out again, I can mark that I need it again and have it moved to a shopping list. So instead of recurring based on time, it would be based on when I mark that I need it again, without having to go to the effort of duplicating the item.