My dd decides herself. And her wake up time doesn't seem to be the factor. She always takes her morning nap, with her pm one it varies significantly, sometimes she'll sleep 1.5 hours, some days as little as 15 mins, an some days she won't sleep at all. either way if she's happy to get out of the cot and is not cranky I let her have her way. She spend the second half of the day in day care and they offer her to have a nap (by putting her down) and its up to her to decide whether she wants it or not.