Never too long without sleep, to be honest, but still intense:
Diablo 1 for me with two friends on a LAN, during summer vacation. They had to drive 5 miles on a bicycle to get to our house. We played from lunch until 4-5 AM, then they went home and came back again the following day at 12:30. Rinse and repeat for a couple of days. We all had sub woofers too, no puny headsets. Weren't necessary anyway, because we were all in the same small room. Ah, those were the times.
Other memorable gaming sessions include
Civilization (never tried any of the sequels) and yes, "
UFO: Enemy Unknown" (aka X-COM 1). That one was traumatizing, but in a good way.
Come to think of it, lots of strategy games were memorable like that, for example
History Line: 1914-1918 (aka Great War: 1914-1918). So absorbing. In way, I can understand PJ's carefulness regarding such games, but on the other hand: I love having the memory and if I could experience games like that once more, I'd do it all over again.
It's funny though, because I'm not into strategy games at all. Then again, the reason for that might be that it's all real-time nowadays, guess I did like turn-based strategy a lot more. Are there any good newish TBS games out there?
I haven't felt the need to play a game nonstop like that in recent years.
King's Bounty came close (still a "perfect game" (tm) in my book).