I always used to go up on the roof once a year to give it a good clean, I used a sheet of 2” polystyrene insulation to kneel on and spread the load, I never had any issues until I managed to knock over the step ladder when up there, my phone was in the house and my wife couldn’t hear me shouting so I had to wait until she came outside. Half an hour sitting on a caravan roof seems a lot longer….
At the end of the day it’s up to the individual but I now find I can get the roof spotless without getting onto the roof. I open all the skylights and use a long reach brush to clean all round them, then close them and clean the entire roof thoroughly using the long reach brush. Finally I wash it with “wash & wax”. I find the the finish looks as good and lasts as long as when I used to get on the roof and polish by hand.
It’s also a long way to fall and my concrete driveway doesn’t look very forgiving!