Around 72 hours. A runescape livestreamer "mr nosleep" did 100 hours straight for some sort of event. Either charity or sub count milestone, I don't recall. By the end, he'd been reduced to mostly standing around or performing low intensity tasks. He was talkative enough at the end though. He said, once 100 hours had been reached, that he was going to go eat a big meal and watch tv for a few hours. I heard rumor he slept for 3 days straight afterwards.