We don't take or make phone calls after 9, and everyone needs to be off the phone by then too.
For the most part, I want everyone in bed before I go...usually 10 PM. The kids are DD (soon to be 15), DD (12), and DS (10). They're welcome to stay up all night reading in their rooms, if they'd like. Oldest DD is the most likely to just go to bed at the first sign of being tired...always the best sleeper, and she babysits almost every day for 3 kids...7, 5 and 2...so she's tired a lot.