8 hours of work, 8 hours of rest, 8 hours of sleep is normal. Nice and symmetrical. Feels like it gives me time to get done what I need to do during the day. I can even deal with 10s, where I don't have much time at home other than to make dinner and get to sleep
12s are unnatural. The shift drags on no matter how busy I am. If you have a pretty reasonable (read very generous) commute of half an hour, it leaves you 11 hours left to cook, keep up on household chores, spend time with family and significant others, and otherwise have a personal life, all while also getting enough sleep that you don't go to work feeling groggy
Fuck 12s