gee, i think everyone is different. My DH gets up early 5.45am to walk the dog, so she wakes up with him and they go out together (he returns her to me at 7.45am). Hence I have a hard time keeping ally up past 6pm as her day starts at 6am with a very stimulating walk outside. do whatever suits your lifestyle. Mornings are teh only time DH gets to spend with her, so early bed early mornings work for us.

I guess what I'm trying to say is each family is different, so I think you need to work out what best suits you all.... But no later than 8pm I would say, or you start to get into trouble when they need to do things the next day or when they need to get up early to start school.

good luck!