Dead batteries are an industry myth!
you just gotta give em a lil kick
I think they can definitely die. No, make that know it's possible. However I think most times they're abandoned somewhere along the 'getting lame' path? As you get less and less runtime (use per charge) eventually you figure it's no longer worth it. So, yes, what an owner might call dead is subjective.
The general failure is decreasing (storage) capacity. The cell that did 2400 mAh when new without issue now strains to make 2000. Since there are two cells in our battery, just like in life in the big city the strong one beats up on the weak one making it work harder still and therefore fail all the faster. Keeping the cells in big battery packs balanced is key to keeping them in service. This means the pack will usually degrade but still be in 'pretty good shape' when the weaker cell packs in and it suddenly fails at a much faster rate with the protection PCB 'firing' more often and sooner.
A new ('better') battery can be faster at heating (especially say the fifth or sixth session.....) but as long as the heater eventually cycles off an old 'barely working' battery doesn't give better vapor, it just might do so half a minute sooner?
The original version, the ones that had a real passthrough function and could run 'PA mode' had the option to remove the aging battery as a factor.
They should get at least 300 cycles under most any conditions the protection circuit allows and not leaving it in your parked car in Death Valley around mid day, but sometime after that it's going to start degrading as the chemicals fail. Lots of effort is expended there, make an electric car battery (which use these very same 18650 cells.....) that lasts longer and you become rich and famous. And adored by women (or men, if you'd prefer.....).
Still, even that is 2,400 sessions (300 times say 8 per). That's a lot of first class vapor for a not very expensive battery....... And I bet on average we get a lot more than that?
OF