When I was 19 I stayed awake once for 5 days, by day 3 I was craving a smoke constantly, always thirsty, day 4 the headaches kicked in, day 5 I really thought I would die so I fell asleep, but 2 other guys in the unit managed another 2 days. Hallucinations after day 4 though, I would never recommend it to anyone, my head has started hurting just thinking about it now 10 years later.