Elfyn-cleaning at height, you cant actually see what you're cleaning.
IMO 50ft you can 'see' higher than that-someone on here has as their strap line
"we clean by faith not by sight when working at height"
same in the dark IMO
Aside, we clean at 5 floors a job in the dark with a street light right in the middle of where we stand, light shining in our eyes, dark everywhere else-can just about make out the glass from the cladding! But we do inside the following day-been doing it 6 years now and it's (nearly) perfect-everytime.
If you're the sort of person who doesn't mind working in the dark-give it a shot, you may make a few $ out of it. It's not for everyone though