I was thinking about this very issue tonight in response to the discussion in
http://forum.sex141.com/eforum/viewthread.php?tid=53199.
I've known quite a few WGs pretty well. In general, they were pretty normal women -- or, at least, well within the range of women who were not WGs. But when they were working as WGs (the good ones anyway!)is they adopted the WG persona... the "I am a wild fantasy sex bomb" image. In part, the persona may be a protection mechanism against the fact that they are nervous, possibly scared, apprehensive about how the session will go... and, yes, possibly exhilarated by the possibility of being the totally uninhibited "bad girl".
It's not unlike an actor in a role. It's not the way they are in real life. Poor Virginboy wants his wife to be the sex bomb she was when she was working briefly as a WG in Hong Kong. But that's not who she really is... So she doesn't treat him that way now, because she views him as a lover, rather than a client.
What you describe (and I have experienced this myself, so I know exactly what you mean) appears to follow the same logic. As they get to know you better, you feel less like a client to them. So they revert from being a WG to being the woman they really are. I don't know that it's necessarily due to the formation of an emotional bond... I think it's just familiarity and comfort. They don't feel that apprehension any more... and apprehension is a close cousin to thrill. You don't feel like a client anymore. You just feel like a nice guy...
And we all know that's the kiss of death...
Have fun, CGP