Did he have sleep breaks between 13-hour shifts?
I’m asking because I did 36 hour duty shifts for two years on an “every third” basis (36-12-12-36-12-12) and I never killed myself.
13 hour shifts are nothing in a hospital as long as, after the shift ends, you go sleep somewhere until the next shift starts.
When I worked in the prison system, I used to do 16 hours shifts regularly, working overtime or swapping days off with other people to hook up vacations. I always tried to get as many of the days I owed them out of the way before the vacation started, so I didn't have them facing me when I got back.
When I became a Seargeant, I used to swap days off with another Sergeant every week. We both had weekends off, so we'd swap to get four days off in a row. We worked 40 hours in 2 1/2 days, each week.