Lithium secondary (rechargeable) batteries, whether replaceable or built-in, can only be counted on for a couple of year life span. It's a chemistry thing. Even unused, and maintained at a reasonable storage voltage, there'll be a decrease in capacity after a year or so.
I know some folks talk about built-in battery mods working okay after 4 or 5 years, but I have faith in science. They may work, but they certainly have decreased battery performance.
Any mod I count on for multiple years out has replaceable batteries, and any replaceable batteries I pick up are fair game for immediate use, since they will drop in performance over time.
(Sowwy for all the posts from me tonight [emoji3])
I have a lot longer experience with cell phone batteries than those in vape gear. The only thing I've learned from it though is that batteries are weird. Some last a lot longer than they are supposed to. And some last a lot less than they're supposed to.