Brides booking their trial nearly always ask how much of the day to keep free. The answer depends on them: on how clear the idea is when they sit down in front of the mirror.
When an hour and a half to two hours is enough
If you arrive knowing what you want, and the photos you have been sending me point the same way, the first proposal usually works. The trial then takes an hour and a half to two hours: I prepare the skin, build the makeup and the hair, we look at the result in daylight, and photos of it are taken.
Why some hair and makeup trials run to three or four hours
Sometimes several options need trying. You may be torn between an updo and a half-up style, or find that the makeup you pictured does not quite convince you once you see it on. Each change means undoing part of the work and building it again, and the trial moves towards three hours.
Four hours come when the work has to start again from scratch, because the first idea does not work and another has to be found from the beginning. That is not a failed trial; it is exactly what a trial is for, and it is far better to find out then than on the wedding morning.
So the trial has no fixed finishing time. It ends when the result convinces you completely, and every bride takes her own time to get there.