Three days. I started to freak out, and starting seeing things that weren't there. Spiders mostly, but other weird things too.
I saw a story, it was a scientific show, about a man who would go to sleep, but his body would not register it as sleep. He started to die, painfully, and very slowly, and the doctors couldn't figure out what was wrong with him. He later went to a sleep study, and they figured it out. He wasn't really sleeping at all when he went to bed at night. He lived with the condition for months before his death, and they feel that he never had any real sleep, ever in his life. It was a disease, actually, with its own name. Can't remember the name of it, but maybe a Google search will help.