Just as with most financial transactions, you get what you pay for. I can see tipping well for excellent service, as you should, but also tipping well just because they've put in alot of effort. If you get very good service and you fall on the cheap side I hope that you are remembered next time you show up.
If you think a place, or a certain provider, shows promise "of things to come" in the future it might be a good idea to grease the rails a bit, too. I know that they remember you (surprised me the first time they said something about a previous visit) and have wondered if they keep quick notes on their customers.
The ladies do talk amongst themselves, too. I had been seeing a certain therapist at one place, went in and she was busy, so I saw a different lady that day. When I went to leave the tip she said "You give ***** a $120 tip." I said "Yes, but she's worked on me more." Told her that if I would see her another time or two I'd tip her better. She seemed satisfied with the answer.
