Wow, this is surprising to me. I guess DH and I have kind of given up. DD1, age 16, is a night owl and procrastinator, as am I, and she doesn't start her homework until late. DH falls asleep early, then wakes up a few hours later, so our house is regularly humming late, late at night.
DD1 goes to bed at midnight to 1 am and gets up at 7:30. She is 16, so 6.5-7.5 hours of sleep. This has been true since age 14ish.
DD2 is in 8th grade and goes to bed at 10:30-11:30 pm and gets up at 7 am or so, so 7.5 to 8.5 hours. She does a decent job going to bed when she's tired, but also puts off doing things that could be done earlier, like showering and music practice. She often breaks out an instrument to practice after 10 pm and acts like I am crazy when I tell her it's too late.
Somehow it feels like less sleep, perhaps because they both sometimes stay up later. I prod them to go to bed, but hey just "uh huh" me, especially DD1. So no set bedtime, but not ideal self-regulation either.
Advice and commentary on living overseas
DD1 15, DD2 12, and DS 9