Many moons ago, when I was a much younger and tougher man, wearing a uniform and playing on a submarine, there were many times I had to pull 24-36 hour shifts of wakefulness. I didn't like it, but there were just times the operational tempo(something broken that needed fixing, drills, drinking binges) didn't let you get to sleep before you had to stand watch again. On in-port duty days, it wasn't unusual to go from 5AM one morning until the some point the following evening with nothing more than a 1-2 hour nap.
After a stretch like that, the goal was to try to get an 'equalizer'....a time you hit the rack right after your 'after watch cleanup' and then slept about 10.5 hours until it was time to wake up and stand watch again.
Yesterday, I had to work a graves/days double shift. I gave up trying to sleep at about 6:30 Sunday night, and finally told my wife at about 8:45 Monday night that I was done, done, done. I was able to get about 9 hours of sleep that way....and it still wasn't enough.
Oh, there are times I wish I could feel the way I felt at 25 years old again...