When to replace Bluetooth headphones?

I have a pair of Bluetooth headphones from about years ago. For some reason whenever I charge them, they seem to have a lot of power. About a couple of weeks ago, I've charged them. For some reason my headphones started to die out on me. Maybe I might be using them too much? Then I have a pet rabbit who chewed up my headphones. Apparently I didn't take care of them pretty good. Keep that in mind that I got them for free.
Answers

spacemissing

Batteries fail. If the headphones are beat up, replacing them would make more sense than replacing only the battery. Keep headphones out of reach of fuzzy friends with sharp teeth.

G. Whilikers

Replace them when they're not doing their job adequately -- that includes appearance and comfort as well as function -- and you can't fix them. If the headphones won't last through a whole movie even when they're freshly charged, it's time to look at your options. That might involve going to the store for a new set, or having someone good with a soldering iron replace the battery.