Camper Vans & Class Ber's only. How late is too late?

I'm not a Class B but, I don't think that really matters.

I think it would be up to the CG management. If they allow late arrivals at 2 or 3 AM, that's their choice.
It's up to the camper to do exactly what you do, get parked as quietly as possible.

You can't always get to the CG earlier because of traffic, construction, accidents, etc..

I don't mind if someone pulls in next to me late at night. I do appreciate it when they're courteous and as quiet as possible.