The battery life in mine has dropped somewhat, but I use only one at a time since I'm not keen on having them transmitting signal through my brain. (I know there isn't science that says it is bad for you, but AFAIK there hasn't been testing of this type of transmission quite so close to the brain.)

One upside of this is that I am charging one AirPod at all times, which basically means I never run out of battery.