I've had two fittings. The first I paid for, because I was having serious problems with my right knee. Turns out that there is a structural difference in my right foot that is remedied with a small shim under my cleat. It was well worth the cost. I learned a few other things that have been helpful. For example, when fatigued, I tend to let my left leg flare out. Knowing this, I've worked on this issue and don't do it nearly as much as I have in the past. The second fitting was when I got my custom built Independent Fabrication built. The shops fitter spent two hours with me making sure it was setup correctly. I checked with the measurements I recorded from my first fitting and they were virtually the same. The only small difference was a two mm difference in seat height.

All of that said, once a good fit is established, I think slight modifications over time are to be expected. I know that as I continue to compress and get shorter with age, there will be a need to make some adjustments. My view is that as long as I have the original measurements from the baseline fitting, I've got a starting point for any tinkering and can always go back to the original setup. Truth be told on some century rides, I stop and make a minor adjustment on the fore and aft position of my saddle just to change positions. It's never more that 2 or 3 mms.