Don't leave a good game, unless you're the reason that it's good

If your stack size is making the game bad, then leave by all means. But make sure you can identify that this is really the cause and not something else. A lot of times, people look at the big stack with more respect that they really deserve to have. If you can keep picking up pots by leveraging this respect, no reason to leave. You just spent the last hour trying to get into that situation.

If people start gunning for you and you don't like to play against that, then leave. I personally like when I get ahead and start to get some chasers. I play smart and agressive and they play for draws and overbet. Over the long run, this is exactly what I want.