My wife and I had a professional fit us to design our custom bikes. He adjusted our old bikes to that fitting prior to building the new bikes so we could get used to the new fit and fine tune before building. As others said - night and day difference. We are both in our 60s and don't expect to see much change in a few years. We use the numbers from the custom fit to adjust bikes we rent or borrow when traveling and that works out fine. I may go back to the fitter in 5 years when I turn 70 just to see if he sees any changes that need addressing.