My parents have accused us (jokingly, I think) of drugging our 18 month old DC. He sleeps between 10-12 per night and 3-4 hrs during the day. However, if there's a lot of action at my parents' when he visits overnight - he sometimes doesn't nap at all. They are very proud of that 'accomplishment'. He will come home and almost collapse and sleep longer than normal. He doesn't seem any worse for wear, but if we go too long on sleep disruption, he will throw his head back and start yelling' night! night!' I feel lucky and would be crazed if I couldn't rely on his sleep schedule.