It sucks to have that kind of work culture, but it's really unhealthy for everyone involved. Is it at all possible to point out its flaws and make everyone's work-life balance better? Or to be the one to work sensible hours and make the rest realise what they are doing is pointless? (I know social pressures like this are very difficult to change, and I'm terrible at dealing with this type of thing myself. I'm actually very lucky in my present job that I can work flexible hours and 8 per day is totally acceptable--I could even get away with less if I really wanted, though I don't.)

I spent a year working 12 hour day and night shifts, so I can certainly sympathise with the hours. I got a 6 mile cycle each way and wasn't entirely desk bound then (industrial laboratory) so physical exercise wasn't an issue.