It varies a lot - sometimes the kids are in bed by 8 and I stay up till 11. Sometimes they're not in bed till 9 and I stay up till 12 and regret it the next day. I suspect as my kids get older (they're 4.5, 2.9, and 0.8 years old atm) that will shift later and later as they converge towards more 8-9 hours of sleep per night. I'm already starting to see it with the 4.5-year-old who will often stay up until 10ish playing in his room. Probably going to need to start allowing him a later bedtime.