I agree Dave, i earn a good wage at window cleaning and dont want the faff of "extras".
When i clean houses at 15-20 pounds people dont mind, they dont see how much you earn as a one man band.
extras are hard work, gruelling on the neck and shoulders, so if you have been established for a long time you should have a band of loyal customers who you only need to clean windows for at a very comfortable hourly rate.
Like you i prefer, if possible to pass them on.
And like you, sometimes i cant wriggle out ie doing a few insides for a lovely old dear whilst she makes a cuppa. etc