When I had two jobs with shifts scheduled with barely an hour between them, I had to stay awake and active for about 75 hours. By the middle of the third day, the sclera of my eyes were completely red, not merely bloodshot, and I wanted to kill everything I saw. When the caffeine finally wore off, I slept on my couch. I went to sleep at around 11:30PM on a Friday night. I woke up at about 1AM. Sunday morning. I was asleep for 25 hours, and I didn't even wake to turn over.
Be sure to get good sleep, and put some money into a good mattress. It will change your life.