LWC
Only other thing you can do is miss em out, when they eventually ask you why you haven't been doing their windows you could tell em in the politest way possible why.
i.e:"I am happy to be your window cleaner as long; as you understand I can not afford to be turned away"
I think this is how i will be doing things more in 2011
Fed up with messer's
Thought about sending letters to not todays; don't think this is worth all the bother and would probably wind custy's up. (who does he think he is, just a bl00dy window cleaner :

)
Think missing em out, shows you are not bothered if you do it or not; and when asked why you've not been back; a polite and firm answer could leave the door open.
Have done this before in past, kept some and lost some

lee