0 to 1. I am 37. I sleep at night. I get up by 6am and go to bed whenever I want. Lately, around 8pm, play some 3DS in bed for an hour or two, then sleep 7 or 8 hours.
In the past, I've tried to nap when I missed out on sleep, but I would wake up with a really bad headache and was useless the rest of the day. I can only nap when I'm sick as a dog.