Our nearly fifteen month old DD usually goes to bed around 7pm. She has a story, bath, milk, teeth brushed then bed. She seems tired but then we can hear her happily chatting away to herself in her cot until almost 9pm some evenings. She never cries and sounds happy. She doesn't usually get up until 8am and has a two ish hour nap in the afternoon. Do we need to put her to bed a bit later?