Good points there.
I'm in the south east, the highest polluted area in the country and it really shows on windows. There's always a layer of dust and dirt around the frames and not cleaning them would be asking for trouble.
Tosh apologies if I came across as being ignorant, I guess when it comes to my cleaning methods I am slightly ignorant in that I think my way is the best way.
There are a number of factors that determine just how quick a window can be cleaned which will vary for all of us, location, equipment used, types of windows being cleaned, the individual speed of the user and we all have our own targets In place.
I just think the best advice you can give someone learning the trade is to concentrate on becoming a quality window cleaner first, it's not good for them or there business to tell them to miss frames or clean windows in seconds. That's something they need to learn for themselves depending on the above factors.