The longest I've gone without sleep is for 25-26 hours. Everyone has a different required amount. If you feel perfectly comfortable with just a few hours, this means your body has naturally adjusted to give yourself more REM time, and less time with normal sleep. If you force your body to have 5 hours, when you're coming from 8, then it will eventually adjust, generating more REM in a shorter period.
Without REM, you basically explode. 
[This message has been edited by youngprer (edited January 24, 2003).]
