Sunshine, if you are taking that long to do a fairly standard semi, you will certainly be quicker just about right from the start.
Ideally you need to tag along with someone for a few hours to see just what can be done and how quickly.
I don't honestly see how it would be possible to take any longer than 20 minutes or so on a standard semi using WFP, even for a complete newbie.
This of course is on a house that is being regularly cleaned, windows that haven't been cleaned for years are a different matter altogether.
This morning for instance I did a first time clean on some flat windows in the middle of our high street.
3rd floor windows and all georgian, they haven't been cleaned since the developers finished work on the site...actually they haven't been cleaned for a lot longer than that, not properly anyway.
10 big georgian windows, and as I said, all third floor and all really dirty.
Time taken; 20 minutes, and every window was cleaned twice, also more time spent on each clean that will be spent on just the normal repeat clean the next time they are cleaned.
Subsequent cleans will be around 8-10 minutes max.
No point comparing to trad, just too high and awkward, sloping pavements, parapets you'd have to climb up on and then drag the ladder up onto and so on.
I also did the flat next to it, 1st floor, 5 georgian windows, 18 panes per window.
Again, first time clean and minging, but only 10 minutes, half that next time.
But it really does depend on the type of windows of course.
Ian