I think most girls, especially agency ones, have roundabout a 2am finish.
This would more than likely be the case with in-calls as they wouldn't want to cause problems with neighbours etc. with noise from cars pulling up at the door and general activity on the street etc.
Outcalls might have a bit more flexibility as regards late bookings as it is the punter's neighbours who are then the ones who might have cause to complain.
Some girls on AW will do car meets and one of them at the dead of night might be great fun.