It took me 35 minutes to clean my 6 windows. I'm much slower these days and I had a few wobbles as I couldn't use my walking stick, with both hands being used to do the job, but I did it and looking at the windows from inside, they look quite shiny, possibly even better than when done by those crappy water fed pole systems!!
My window cleaner uses a pole and imo does an excellent job of it. I have quite a big house with an extension plus conservatory. He charges £12.00, money well spent I think.