TouchID was definitely one of the "must-have-new-phone-now" features that also triggered a buy for me. My iPhone upgrades always happened due to killer feature

TouchID was definitely one of the "must-have-new-phone-now" features that also triggered a buy for me. My iPhone upgrades always happened due to killer features (for me at least) being introduced. When I upgraded, I always bought the most expensive option with the largest flash memory built-in because I wanted these things to last until the next killer feature was ready for mass market, and the periods in between every device have been getting longer every time. iPhone 3G (3G networking) -> 2 years -> iPhone 4 (retina display) -> 3 years -> iPhone 5S (TouchID) -> 4 years -> iPhone X (FaceID and full-front OLED)