Haven't reached my first anniversary yet and my first WG has retired. At the time thought she was amazing, but experience has shown her to be just OK and too expensive, although I did see her again before anybody else. I do look back fondly though.
As far as celebrating goes, I pop my cork on every punt!! If I were to celebrate anything it would be my regular; just booked my ninth visit, and hoping like fuck she doesn't retire as she has told me a promotion at work may see her travel more, have less time and earn more money, so less opportunity and inclination to carry on as a WG. I booked 2 hours, so if its my last visit I'm going to have a party with her!!