How much sleep

How much sleep do babies, toddlers etc. need?

When Tristian was first born he slept almost 20 hours a day. He would wake up eat and then go back to bed. This lasted til he was about 4 months old and then he would slowly sleep less and stay up more until now he sleeps about 10 hours at night and between 2 or 3 hours in his afternoon nap. As soon as Tristian wakes up at around 8:00am, he is wide awake, funny and not tired a bit. After about 4 or 5 hours he starts fading and really needs a nap because he starts to get cranky. He will go for 2 or 3 hours and wake up feeling great, funny and happy. After his afternoon nap he plays and plays and plays and plays and doesn't ever get tired out. By the time it's bed time he is not tired one bit. We bathe him and lie him down with some milk and he seems to get a little bit tired but once he gets up to his room he just wants to play again. I don't know if we are letting him sleep too much for his afternoon nap or if we should run him in a hamster wheel to tire him out. He eventually falls asleep but after at least a half hour.