while being paid for sex gives me no moral qualms at all, other things do.
I'll assume that you're being honest! If so, whilst I think it shows you in a better light, it's also singularly, naive, from a business perspective! Prostitution is a service business, first and foremost. I already know that you're experienced, both in age and in this business. I've read your profile and some of your more lively posts elsewhere!
It seems to me that the only thing you're duty bound to point out to these guys is that it's just that. I see no reason why you should stop seeing any punter, unless you thought they'd crossed your own personal boundaries so much so, that you felt uncomfortable. If you're simply trying to second guess and stop them feeling 'hurt', I wouldn't bother playing that game. You may well end up hurting them even more by refusing to see them!
I have this nagging belief that whilst you may well be happy right now taking the cash for sex, you harbor long term doubts yourself, about being in this business? Perhaps I'm wrong on that?