As someone who has done both for years, stick with the three twelves. It is much less stressful and you get nice long stetches of time off. Sometimes I take 25mg of bendryl when I get home in the morning, especially if I have to go back in that day. I sleep until about 12:30pm, eat a small snack, and try to sleep more before I go to work. When I was single, I stayed up as late as possible on my nights off, but now with a family, I go to bed at a normal time and it seems to work. Yes, I do get obsessed with sleep when I am off. It's a lot nicer in the hospital at night - a much nicer routine.