I once went 44 hours without sleep in my late teens, and another time for 42 hours in my mid-20s in University. By the end of the latter, I was hallucinating things that weren't happening. Nothing too creepy. I go 20 ish hours a few times a year, when I'm traveling to the west coast and I have to get up early on east coast time, but then am up late on west coast, which adds 3 hours to my day.