i stil have my first ones from about 10 months ago. still working fine but i rotate more them 2
it depends on how hard you vape, the voltage you vape at, and how good your charger is, as well as some brands just arent as good as others ( you didnt say what your using im guessing the aw's?).
im not sure about the 500's i only use 650's but im sure your charging every day?
which charger the provape?
i would check them with a meter as soon as they come off the charger and make sure they are 4.2 (4.19)v fresh.
some chargers are harder on the
batteries then others, a slow charger may recondition them for longer use.