Or for people who work 6 am shifts multiple times per week, and start work at 9 am the rest of the time. I could conceivably stay up til 2 am partying if I stayed up til 2 am every night and didn't have to get up until 10 every morning, but the real problem is that I can't get up at 5 am on a Friday morning and be able to stay up late on a Friday night. I could conceivably change this by working fewer opening shifts and more evening shifts, but I like getting up early and then having my evenings at home.