Waking baby up?

How long do you let your baby sleep? My son normally sleeps 830-830 but we didnt get to be until 930 last night. Its now 1115 and he is still sleeping. He did wake up to eat at 4am and then again at 830 which is his normal wake up time but today he went back to sleep after that. Im more than ok with 12 hours of sleep but i dont know if its ok to let him sleep longer than 12 hours? Anybody else have a baby sleeping longer than 12 hours?