It can be a bit too easy at times once you've got a good system going and everything working smoothly, especially on maintenance cleans. I find I'm in and out so quick at times customers sometimes question whether I've actually finished. If this happens then in a friendly manner I just invite them to check their windows. It's not usually a problem once they have checked - if they check.
I've always enjoyed window cleaning, but I enjoy working with wfp much more than I ever did with trad tools and a ladder.