If you don't count my original Kodak Instamatic, I forget the model, it used the 126 cassette, and my Olympus XA2 compact, I have changed camera mount twice in something like 45 years. I started out with M42, and my Dad's hand me down Practica Nova. Then when I was 16 I got a brand new Pentax ME Super, and so moved to K mount. I stayed with the K mount, adding both Ricoh and Chinon bodies until 2005.
In 2005 I switched to digital, and Canon EOS, with a 300D kit from Jessops. At the time the Pentax digital offerings were pretty poor, and nothing competed on price/quality with the 300D. Also not in Pentax's favour was the ramifications of their slow development of the K mount. All of my MF, and mechanical aperture K mount lenses were essentially completely unuseable with the modern film/digital AF bodies. Unlike Canon when you fit an adapted MF lens, the Pentax doesn't even like you using the metering system in Manual, let alone doing autoexposure in Av. So since none of my old MF film kit was going to be useable switching to Canon was actually more cost effective.