Dryden on 11 January 2008
Geez, I don't know because I've never watched the clock, but I've done LAN parties with everything from Rise of the Triad to Quake to Unreal Tournament for well over 12-14 hours. There was a stretch in 1996 or 1997 maybe where I did some mod and level design work on Rise of the Triad for nearly two days straight. I did some level creation on Duke Nukem 3D that caused me many sleepless nights, too.
Going back to my school days there were a lot of missed classes staying up all night drinking beer and playing Madden or General Chaos on the Genesis, or Super Mario World and Mario Kart on the SNES.
I might have missed a couple of days worth of high school when Final Fantasy came out on the NES too. :/
