Just coming at this from someone who is not that much older...it used to annoy me so much when my dad would tell me to go to bed. When I was 18, that was the first thing I told him was going. I remember sitting downstairs on a Friday night and him telling me I had to go to bed. I was 18. I told him as an adult, I was perfectly capable of making my own bedtime. I mean, that was a point of contention for a while. Now, he doesn't do that to my brother, who is 17 (and on the autism spectrum). I think he learned. We kind of figure with my brother that he can figure it out, and if he's sleepy the next day, he'll learn.