"Hanging out" past the summer is not all its cracked up to be. The summer up here in Annapolis was awesome, stash job was easy and finally got to make up for my lack of a "real college experience." After it started getting cold though, no more wake-boarding every afternoon, or sailing, or other ensigns to party with.... Also you find yourself wanting to get on with it. I had no choice due to medical reasons, but if I had I would have tried to go down in September.
edit: Though I guess if you were to be stashed in a real college town partying ould possibly continue past the summer.