I have a very erratic sleep schedule, mostly due to ADHD...the H part prevents me from falling asleep when I want to.
Understanding the importance of sleep, I did some research on sleep cycles, and ran across this:http://www.dreammoods.com/dreaminformation/dreamresearch.htm
Yeah you do need 6-8 hours of restful sleep every night, but if you understand the mechanics of sleep you can alter that to fit your needs. I often go through only the 4 primary cycles then wake up without repeating them...then drink a glass of water and do it again for a short nap, short because the cycles are faster. It's not as effective as sleeping the full 6-8 hours, but in a pinch it definitely works.
About once or twice a month the erratic sleep pattern will catch up, and without warning I'll sleep straight through the entire 8+ hours without so much as twitching a single muscle, waking up in the same exact position I passed out. That's when I feel the most rested.
Basically if you understand the sleep cycles, you can work with less sleep for a limited amount of time and still make great progress with fitness. It's all in knowing how your body responds. If you know you haven't gotten enough sleep, don't workout cause it will only make you sleep worse the next night (or day, or evening, or whenever you fall asleep).