I think the key to having a life...
... is making sure you don't feel trapped in the squirrel-cage. I also enjoy doing some work-related things, like reading a book on programming, for instance, when not at work. But if I start to feel that it's something I should do, instead of something I want to do (in my off time), then I'll drive myself into the ground. Did that once already -- it cost me my job, my marriage, and a good part of my sanity -- but I came out better on the other side.