I have two jobs that are cleaned every 4 weeks.
The 2 jobs I have use to have a window cleaner but sacked them when they got sc glass. Both customers had the glass installed 8-10 weeks then I got the job of cleaning them due to the mess on the windows.
I use a super-lite brush on both jobs and they come up great each month. one of the customers got ripped of by the sales team that fitted the glass as they are an old couple. the sales guy said you will never need a window cleaner again! But when you see the house you could understand why the glass actually would not clean at all.
The ground floor windows have a 2 foot sofet that leads out, meaning that no rain could ever get to the glass.
What a waste of money