Trad or WFP, I don't think there's really a difference that matters when it comes to frequency.
I think as a rule, the better your prices the less frequent you should be. The bulk of my work used to be done calendar monthly and as my prices increased so did the 'Is it that time already?' comments.
So for the past few years I've been taking new stand alone jobs on at high prices and I push the long frequency (8 weekly) as part of the sell, and I find it works well. Customers seem to be generally more inclined to accept the higher price at a less than usual frequency, and they seem happy to see us when we arrive to clean their windows.
And I'm probably more like 5 or 6 weekly for my 'monthly work', which is great, because I think I am at the edge of what I can reasonably charge (well that's my perception; I can't say for sure) without giving them resentments and looking for a new cheaper window cleaner.
I cannot imagine cleaning domestic properties every-two-weeks, for those window cleaners who do, don't your customers get tired of seeing your ugly mugs looking at them from their already clean windows?
