Sleep deprivation can really take a toll on the body. Taking stimulants around the clock can without sleep can cause heart problems. I have seen this in patients. The brain's frontal cortex relies on sleep to function effectively. Insufficient rest adversely affects the frontal cortex's ability to control speech, access memory, and solve problems. The effect on physical energy is also startling: otherwise healthy people quickly show symptoms of age and early diabetes as glucose metabolism falls by up to forty percent. These physical reactions disappear when the test subject is allowed to rest properly. Not to mention...Driving and other activities can become dangerous without sufficient rest. It is not worth the risk. Now, with that said...the military uses sleep deprivation in training sometimes and they also use it as a way to interogate someone. I believe more than 72 hours is very dangerous.
Geoff