I used to work at a startup where this was the case, but I've since changed. I love my work and my co-workers and I think they all work extremely hard, but I go home every night at 6:30. I cook for myself. I take salsa lessons. I read. And I work on my own projects.
Interesting work at companies comes with ebb and flows. Sometimes you work on things you don't like, sometimes you get bored, but if you keep your mind fresh and sane you'll come up with things to work on that are meaningful and interesting.