how old is it ?
have you been draining it farther before charging ?
more dis-charged = more time to re-charge
do you pay attention to puff counter vs battery life ?
have you been playing with it more than before ?
did you get a new topper/tank with different Ω's ?
new juice maybe that makes you 'crank' the power up more ?
just a few things to think about so maybe you can find a reason,
if not, play the"
Maybe it's in my head " card
