High/Low Mileage

This is kind of related to a discussion that SlickSpic posted about 2nd chances. However, it is a reverse situation. I have at times been the "victim" of what I can best describe as a damn good lapdance that promises more of the same but ends up being the best I'll ever get. Sometimes, a dancer will give me an awesome lapdance with all kinds of play the first time I see her. However, on subsequent visits, I am given a less-than-stellar repeat performance. And, of course, stupid me, I keep hoping that the first time wasn't a fluke. It's almost like the game of golf - you make that one awesome swing and the ball flies true, and you spend the rest of your life in search of that one true swing again. My question is: have any of you had this scenario, and at what point do you cut your losses and say it's never gonna happen again?