Are you looking for a good quality massage session? If yes, move on. Because you will feel your time wasted and 15 minutes will feel like an hour cause it's that dreadful. You will question in your head that you can do better from your experience.
YMMV after if you are clean, polite and nice to her. Otherwise, there are other places to try.
But if you just want to try once only, go for the 30 mins maximum cause that alone will feel like 90 minutes of "is this going to end soon?"