Jim, I have had that experience a couple of times in strip clubs, during "private" booth dances... in one occassion, I found out that a girl was a female ejaculator... alot of fun, especially when you come out of the booth soaking wet from chin to knees... she wasn't counting dances, she wasn't anything except enjoying getting off a few times...
I have also had an out of twon experience, while in Vegas. Got a few dances from a nice asian girl, schoolgirl uniform costume, in a VIP area. The dances were good, a little naughty, but not too far out of line - this club had bouncers watching the action in the VIP and applying the rules closely.
However, the girls would also do "table dances", basically grinders in public. After having been out of the VIP for about a half an hour, the girl comes back up to me, and says "I am going to dance for you now, come with me" and she takes me to a seat against the wall, also against one side of the stage. She climbs up on top of me, and without removing any of her costume grabs my hand and sticks it down the front of her panties... she whispers in my ear "I'm so horny, make me cum so I can go home and sleep well!" and won't leave me until I give her a resounding ring of the bell - in a VERY public area. After her breathing came back to normal, she thanked me, gave me a kiss on the cheek, and WENT HOME... no charge...
not sure about nympho, but I love cases of "just want to get off!"...
MATt