I switch when I find something that can improve ball striking, distance, or, consistency. In 2017 I broke from that trend and bought a set of C16 and 718 AP1. Aging with a bad back, C16 have Modus 105 steel, 718 AP1 have Tensei graphite for those days when my back can't tolerate heavier and firmer steel shafts. It has made it possible for me to play on days when I'm less than 100% without a lot of pain afterward.