Sleep is a necessity, just like eating/drinking, breathing, and going to the bathroom. Go without doing any of these things long enough, and the body dies. That's just how it works. Humans simply can't go for weeks without some kind of sleep (let alone years!). You would need tremendous willpower to even last more than a week before your body would shut itself down for you.

As for me, the longest I have gone without sleep that I can recall would probably have been around 42-44 hours. Even at that point, I had some peripheral hallucinations (mostly shadows taking forms that I thought were people, etc.). As someone who avoids drugs of any kind like the plague, I do not seek out hallucinations and avoid staying up for too long.

I also find that while it is said that teenagers require a good deal more sleep than adults, I find that I personally need more sleep as I age than I did as a teenager. Back then, I could stay up as late as I wanted to with no problems. But as I got older, (and especially once I gave up caffeine - a wonderful move which I recommend to everyone) I found myself needing more and more sleep. It used to take sometimes hours for me to get to sleep (before giving up caffeine). Now, it still takes me longer than is average to fall asleep, but it's a lot quicker than it used to be. And I'm a very deep sleeper as well, and it takes me hours to fully wake up, really. I mean, I can function, but not well, and not with a good attitude.

Ideally, I'd sleep 14 hours a night. Right now, I get between 9 and 12 depending on whether I have the free time. I'm a zombie if I get less than 6 hours. I guess one's ability to stay up (and how fast they wake up) is determined by the amount of chemicals their brain produces to wake them up, and the rate at which those chemicals are produced. I probably have some sort of deficiency there, which would explain my need for long periods of sleep to function properly, as well as the long amount of time it takes for me to become alert after sleep.

But I love sleeping. If only humans hibernated during winter, I'd be all set.

Sleep deprivation caused one of the most beautiful experiences of my life, and then I lost my mind.

It was summer and I had turned 18 the previous winter and decided to finally get away from my piss-ache family and live my own life. It almost worked out too. I moved in with a friend, who was living at his deranged aunts house for free. The time I was there I didn't have to pay rent. I know this sounds like a crazy situation, and it was. The reason I picked that place to live at was because I literally had no where else to go. And I was desperate to get away from my family because they are evil. And I mean literally evil, like Satan himself. I won't go into any details, but I'm still suffering from the things my family has done to me.
The reason I was friends with the guy whose aunts place I moved into was because they had all the same issues I did, we broke the world in half so we could carry it together on our shoulders heavy issues. Seriously, you don't want to know. Anyway, this friend was a total night owl, and I was on a completely haywire sleep schedule already. I've had insomnia since I was about four years old. I wish I was joking, but I'm not. I have bouts where I sleep normally, but insomnia is my regular way of life. I can't handle routine. That's why I'm posting this at four in the morning. Anyway, I would regularly go about 36 hours without sleep and then I would completely crash out. This was not a problem for me, as I was not working at the time. Also, being away from my family, who I didn't even talk to or phone or email or anything for a full year was causing me to confront many of the issues I had. Unfortunately, after losing the apartment that I later got, I am now again living at my fathers house. I have almost completely regressed. Anyway, the problem started when my friend kept waking me up about five hours after I crashed so that we could go do stuff. This stuff included rampant drinking out in public in the middle of the night, climbing buildings parcours style and running from the cops. It also included going to the playground of a local catholic school and screaming random obsenities. "Satan, come out come out wherever you are!", or whatever other sick #ed up # came to our minds. One of the times we were yelling I randomly screamed something out that had been trapped in my psyche to the point where I had forgotten all about it. It was sick, #ed up # that had happened to me. The memories started to come back and I didn't sleep for two and a half days. Then I finally crashed out, and about four hours after I had crashed out, the doorbell rang and I woke up. Across the room from my bed, there was another bed. It looked like a hospital bed. On the bed there was a giant rat about twice my size. It looked sort of like the characters on Pixar's Ratatouille. However, that is not where my mind got the imagery, because that movie was still years away. Anyway, this rat had a baby rat about the size of a child and it was reading it a bedtime story. I was glad that they were there because I was feeling so lonely at that time. All of a sudden a giant hideous moth flew from somewhere behind me towards the rats. All of a sudden the little rat jumped up and down on the bed, and picked up a tennis racket, and in German yelled in a playful voice "Schmetterball!", and swatted the moth with the tennis racket and the moth went flying out the window. Then the rat crawled back into its bed with its mom and I decided to go back to sleep, because this was just a little too much for me to handle at that point. I have tried to recreate those results with more sleep deprivation since then, but to no avail, because I have no external source disrupting my sleep, at least not aggressively enough to make me actually wake up. Anyway, my friend told me the next day that he had opened the door and then decided to let me sleep because I looked like I was tripping. I had been trying to say hello to the rats, apparently. So yeah, I think that unless something is extraordinary about your biochemistry, or you are very spiritually enlightened, going without sleep for extended periods of time is a bad, bad idea.

I've been awake for 84 hours solid, when I was studying, looking after my little kids, and was offered the opportunity to work as a nurse for three nights when I needed to pay off a stack of bills. That last day, trying to stay on track because I was busy until evening, was a nightmare.

A bunch of Victorian firefighters were also awake that long, a few years ago, as arsehole arsenists kept lighting fire after huge fire. All the CFA were called out and they had no chance to rest in between fires. Some learned their own houses had burned and their loved ones died, but, despite being volunteers, they continued to do the impossible and keep fighting to save other families.

In the end, you are just walking will-power.