Originally Posted by Léo Ho Tep
What would he have to watch over? People forgetting to bring back books in the library? There was nothing to watch over.
Yup. Also, the fact that Alfred says "you haven't been down here for a long time" seems to imply that Bruce did in fact spend some time keeping an eye on things after TDK. After all, the mansion/new cave wasn't even built at the end of TDK, so sometime after that we can assume he spent at least some time in the cave keeping a vigilant eye on the state of Gotham. Eventually it becomes clear that he's accomplished his goal of stamping out organized crime. He can't move on though, and is just waiting and waiting for the next "extreme" threat to arise, and eventually it does with Bane.