sleep issues

Here I sit at 5am watching my kiddo play. I know that at this age they are supposed to be sleeping in 10 to 12 hour stretches. I knew last night when he went to bed I would be up early. It's like he's programed to wake up after 8 hours. Must nights he won't sleep until midnight and he's up at 8am sharp. Last night he decided he was tired at 8. His normal day is bed around midnight. Wake up at 8. A nap between 10 and 11am that lasts approximatly 3 hours. Another short nap around 6. Then bed at midnight. I hate being up until midnight but if I put him to bed earlier he's up at 5am. Any suggestions on how to help him sleep longer? He's got a white noise machine, he's been sleeping happily in his own room for months and he rarely walks up in the night.