I tried how far I can push it. So I tried going without sleep as long as I can on one occasion, and on another occasion i wanted to see how many days i can last with only 3h of sleep per night.
I invited some friends who took turns in playing videogames against me. The first 48h were easy, the next 12h interesting, and after that i started napping if there was a too long break inbetween the curves in racing games. ^^
Sanitywise i think i kept getting more irrational and less focused.
On the other experiment, I kept feeling better till around day 5. afterwards it just grew worse till on around day when I quit I felt completely listless and apathetic.

Don't think I can keep up with my current sleeping tables another 10 years though. My mom said she used to be like me, now she sleeps like 10h average per night on weekdays. XD god i hope i won't turn out that way... sleeping half of my life, what a waste of time. =P