i dont know if its normal or not but i was told by a lot of people it takes up to 3 cleans for them to come right coz of dirt dripping down afterwards from vents etc, so ive just tried to counteract that by doing the 3 cleans first time, but when the 2 of us where working together last week for our 1st week on wfp we made our normal daily target and a bit more every day even doing them 3 times, not 1 single complaint and i also told every customer to call if not quite right, not 1 call, so i figure next month on same houses we can do lots more by only doing each window once