I have recently changed back to 12-hour shifts, and the maths is pretty tight. My commute is just under an hour, call it an hour and a quarter between getting ready to leave home and arriving at my desk ready to work. When I worked 4 x 10 hours, it was OK, but the extra 2 hours a day makes things very tight, time-wise. As others have said up there ^^^ once you factor in sleep, meals, washing/showering and changing, plus a bit of social time with your nearest and dearest, there isn't a lot left. I get home about 7.30 am, have something to eat and chat with the wife, and I am in bed by about 8.30. I have to read for a bit (to wind down) and then sleep from about 9 am to say 4 pm. Up, shower, something to eat, a bit more conversation, and I am off to work at about 5.30. (I do this on alternate days, and use the car and have a swim on the days in between.) I probably need more sleep than that, as I get very tired and this affects my ability to sleep on my days off. Strangely, rather than catch up with a 12-hour snooze session, I find I can't sleep more than about 3 hours at a stretch on my days/nights off. Any increase in working hours, or a longer/slower journey, and I would definitely not be able to sustain it. For me, a 90-minute commute would make it impossible.
I look back to the days when I did 5 8-hour days a week, and wonder what I did with all the time!