There is no reason to change them out once a year if they are being treated properly. Some of my
batteries are going on 3 years old now and they are still working.

Same here. I have 2 or 3 AW 18650 IMR 2000mah 10 amp batteries which are
nearly 3 years old in rotation for my Provari's. They don't perform like they did when they were new, but still perform for nearly a day's worth of vaping.
I firmly believe if you keep several batteries in rotation, and allow a few hours "rest" after the charge cycle before using them, and don't over-discharge them, that batteries will live a longer life.