What the longest time you've gone without sleeping

56 hours.

about 40 hours, never again, I need at least 5 hours of sleep a day.

Longest was about 38 hours.

Last year I found out that if I'm camping in the freezing cold I can still function properly from 4 hours' sleep over a span of 3 days.

52 hours...

Probably 24 hours most. I can't remember.