[cmrocks]

I find that my sleep requirements depend largely on what sort of activities I'm doing. When I was working at the gold mine, we worked 12 hour days, relatively physical work and would typically hit the gym after work for an hour. Not a lot of mental work involved. I would get by just fine with 6.5 hours a night. Now, I'm back in grad school and I work on a computer all day and have a very mentally demanding job. I find that I need 8 or 9 hours of sleep to feel refreshed.