3 cleans to get the windows right isn't about how long it takes wfp to clean a window,.. but more about how long it will take a newbie to figure out how to work WFP properly!
I do a lot of one off work & first cleans,.. I can honestly say that I never leave a house without checking results, and while I do have to re-clean the occasional pane, I never leave unsatisfied with my work. I also offer a 100% satisfaction guarantee & make a point of telling custies that I'd rather make an extra trip back to re-clean than get a reputation for bad workmanship. I get maybe 1 callback every 2 years,...
If you can't get it right first time, go working with a friendly WFP'er for a couple of days,.. free labour in exchange for knowledge. You can't beat on the job learning.
Nat, maybe as you claim to get windows right first time (and I'm not doubting you), it would help the less experienced guys have a better understanding if you explained your technique.
I have a hot system which is defo a huge advantage on first cleans, and I use quite a high flow rate, about 2.5 litres per minute on first cleans,.. I scrub the frames really well first, all round the house (and give the glass a quick wipe) then go back & do the glass properly without touching the frames making sure to rinse loads. By the time you're on the last window the first few will be dry enough that you can see if you're likely to have problems,.. re-clean any that need it. I use Gardiners SL brushes.