"the proper way"
Macc your windows must be almost spotless before you start - easy peasy! Don't your customers notice that they don't need doing?
Mine are all 4 weekly as well. It makes it real easy wfp. Some have noticed that they stay clean in between cleans, but the way I see it is, well who wants their windows to be dirty at all, if they wanted their windows to be dirty for a couple of weeks every now and then they wouldn't be paying for a window cleaner.Simon.
I clean windows however often the customer wants. The method doesn't matter.