Like I said on Darthkenobi0's blog entitled "Crazy Shit We Do!", the longest I've ever played a console non-stop for was five hours. Yep, a few years ago (the exact year escapes me just now), I played my PS2 from 10 a.m. right through to 3 p.m.
So, what's the longest you've ever played a console non-stop for? I'll be impressed if anyone can beat five hours!