We currently have three rating metrics, one for the club, one for the value and one for the dancers. I don't put much stock in these ratings when I'm researching a club. Nothing substitutes for reading reviews about the club and the dancers.
However, I would find a "mileage" rating to be at least as valuable as the other ratings. I acknowledge chessmaster's comment about ymmv but that very same issue also applies to the other ratings that can vary from visit to visit (e.g., ratings of value and dancers will vary between visits to the same club).
The only down side to a mileage rating would be if the reviews linked dancer names to very explicit mileage ratings. I would want to protect the identity of dancers who provide exceptional service from management (especially if it was a no extras club and the dancer was pushing the club rules).
By the way, I have a policy of not identifying dancers by name if I provide much detail about the level of service in the club. If I do mention a dancer by name, I only provide vague details about the level of fun that was provided, unless the dancer has actually asked me to include details in a review. I do make an exception to this general privacy policy. I will identify ROBs and very poor performers as a service to fellow mongers.