I've pulled more all-nighters than I can count, many of them were playing FFXI.
The longest I think I've actually played a game in one sitting would probably be Metal Gear Solid 2, which I played for 11 hours straight one day. I stopped playing almost at the very end of the game, because the game actually told me to turn it off. The commander guy actually called me on my codec and said "You have been playing this game too long, turn it off now.", and I actually complied and turned the game off. The next time I played, I realized that he says that no matter how long you've been playing, and I was kind of disappointed.
