Where are you based? They’ll be loads of groups out at night round the edge of the Peak, 50 maybe 100 per week probably, because that’s where people live and the Peak is big.
If you’re talking about getting into the heart of the classic Edale / Hope / Ladybower stuff at night then that’s going to be less common as a regular thing. It’s too far to reach riding out of an evening from somewhere civilised, and most people aren’t interested in a drive out after work for a night ride. Saying that, I bet there must be at least a couple of night rides that go out regular from Hope, say.
If you fancy it then just have at it – no barriers to doing all of your favourite trails at night. Just take it steady on the technical stuff if you’re on your own.