Is it bad for a 4 month old to sleep over 12 hrs, everynight?

My son sleeps At 10pm and doesn't wake up until 11am sometime 11:30. Since he was born he was always an awesome sleeper. He use to go to be at 11pm and woke up at 7 am. I m just wondering if that is bad or its okay. He doesn't seem to have a problem with it, he is always happy, never crys, only when its time to feed.