I started my nursing career a long time ago, and we worked 8 hour shifts, 5 days a week. I did that for 8 years. When our unit introduced voluntary 12 hour shifts, I decided to try them, and loved it. I always worked nights, 7pm-7am. And yes, you really are at the hospital for longer than 12 hours. It was worth it to me to have the 4 days off in between.
Some nurses worked Mon,Tues,Wed. one week, then Wed, Thurs, Fri, the alternate week. So they would have 6 days off in a row every other week.
When our hospital started offering Weekend Option, I signed on to that contract, working every Saturday and Sunday. Nurses could also opt to work every Friday/Saturday. When I developed arthritis I worked every Friday and Sunday per MD orders, with 24 hours off between shifts.
It was exhausting. I always had a cold drink with me, and snacks in my car to munch on during the drive home. Luckily I only lived 10 miles away from work. But we did have a nurse and her mom who would drive in from out of town to work weekend option + one extra shift each week. They were involved in a car accident one day on their way home, and after that they stayed at a hotel for a night after their shifts, so they could rest.