James isn't leaving an area much wider than a few miles around his house, if he can help it. There are still a lot of empty apartments, which means plenty of food. Sure, most of it's gone bad by now, but he really only needs to find one or two apartments with anything in them to last him for a good amount of time. 
Anyway, what I'm getting at is that he isn't very well going to leave unless it's imminently necessary. Or if someone could persuade him to.