Well, I don't really have too hard and fast rules.
Generally when I take on new residential work they ask how often I will clean etc. I tell them I prefer once a month and all year round and I only stop if the rain is too bad. that sorts most out.
The ones like you say are few and far between, some I have dropped, some, I put up with because I have priced it accordingly. I have a handful that call me whenever they want me, mostly quite big country house types, "if the price is right....come on down!" But there are the odd ones who are bread and butter price to start with - can't really justify being messed around too much by that kind. But I usually try to explain it fairly and reasonably. I tell customers I don't just come in the summer, this is my business, my living, I depend on it, I provide a year-round maintenance service!
Some say ok, go ahead, once it's explained, some still say no, I don't think any like that have ever had the nerve to call me again.