Trust the technology

As I say in my bio I am an avid pure water user. Despite that I will, at times, find myself thinking to myself - will this work? As an example we did one of our largest residential clients homes today. It took me 7 hours on the outside the first time using a ladder (32ft). Today it took me 3 hours. This home is about 4 years old and has divided panes, huge circle windows, round tops, and on the back it's about 40+ft to the highest window. It's a perfect candidate for pure water technology.
As I'm doing the job I keep having those nagging little thoughts - will it spot? Will it have streaks? You know the voice. I call it "the doubter". After the job I checked over this 3 story monster and found one streak and a couple of spots that took me a total of 5 minutes to fix. Even the client was awestruck at how we could let the water dry on the windows and get spot free results. That's usually the point where that little voice changes to a bigger voice saying - "I told you, trust the technology"!