Well personally i start to be a bit used up aswell, not by the work i still love, but by my situation. I have been in 3 companies for the last 5 years. One which closed after my 6 months contract, another ran by gangster bosses in Paris which closed after 2 years (lots of adventures) and Creative Assembly in England which was more solid but which i left after 1 year.
And well when i began working i didn't mind moving, but nowadays i start feeling the effects : for one I have my girlfriend who doesn't like relocating so often or having an ocean separating her from her family, and on the other side my parents who are getting older and all the consecutive health problems ( 77 - 75 years old respectively ) and since i'm their only child i feel i cannot move as far away as the other side of the world. So there's that which have been a great burden for me when i was in England for a year to try out the foreign worker experience. Especially since CA is located in a small isolated town, and although I may lived the worst that can happen to you in Paris work wise (everything we made thrown to the trash, and the studio quickly degenerated into an extreme version of the raft of the medusa) i have met some awesome friends and paradoxically had a really great time getting my work done in this agitated challenging environment. At CA things were running smoothly (more or so), i loved the franchise i was working on (big total war fanboy) but god the atmosphere was depressing, I have no idea what was going on in this studio, everyone was super nice but somehow found human interaction awkward, they just started their day sitting on their chair with a timid "morning" (and so i did), went for the microwave for lunch and left work without a word. God the cold shower i took on my first days when i was used to see clashes between people out loud in the open space.
So maybe i'm unlucky, maybe i'm looking for it. I still love doing environment art but like 3dnj said, you have to find your balance. And today it's not really the case for me and i'm getting a bit used up :/, i'm considering starting studies again to do something else, but really that would break my heart.