I found changing nap time helped. When dd1 was younger she would go down at 11. Then there started to be issues so we moved it to 1. Then she started up again so we dropped it completely. Now some days she has a nap, some days she doesn't - but if she does she goes at 11 - and she usually asks to go. I prefer the days she doesn't have one cos if she does, it's soooo hard to get her to sleep at night!