It actually became very weird, I was sleepy during 24-36 hours of no sleep then I liked the feeling. I even had some hallucinations on the 3rd day, so my friends forced me go to room and sleep. If they wouldnt I would have stayed awake whole 72 hours lol.
I once stayed 40 hours awake without any sleep, around the 30 hr mark, I did not know whether I was walking or sleeping LOL