Firstly: Your "monies worth" should be based on the time you spend in the escorts company, not how many times you blow your load. I imagine theres many a guy who says he wants to cum again and it takes forever, hence why it may be frowned upon by some escorts.
Secondly: If its a good appointment you should be satisfied after one cum!
Thirdly: Id never have time to go again, what with the one hour nap needed post orgasm