I used to get around 4 when i was a kid, i had insomnia that i know now wad due to having Sleep Apnea.
I now average around 6-7. but have found that if i can get 9 hours every night (and it has to be routine) then i feel amazing.
Most people i know try to act macho and say "Oh i only need 5 hours of sleep (or 4, or 3 or whatever)" or they'll say "I feel worse if i sleep 8+ hours" the thing is. Your body wants/needs 8+ but it has to be in routine. If you are averaging 5 hours of sleep every night then try to get a 9 hour night, you're body will put itself in a deep sleep mode you're not used to, to try to get as much use out of that 9 hours as it can, so when you wake up. you are not rested, you slept to deep.
Personally, i hate the feeling of "surviving" i'd rather feel "good" and if you get 8+ a night, EVERY NIGHT you'll feel way better. (its mostly about routine.)