She varies a lot. Sometimes it's only half an hour, other times it's 2 hours. She's great in the mornings too. We're not really sure what time she wakes up but she's happy to play/talk to herself in her cot til she gets bored and starts talking to us.
Today on my first day off for Christmas she woke up at 8ish but went back to sleep. I didn't hear her again til 9:53 so had a lovely lie in :D