The PA2V2 finally ran down today after 27 days of use. The past 10 days I was thinking, since I use it daily for at least 3 hours, the battery was never going to run down, so I left it on 24/7 for those 10 days and it finally started breaking up.
So it's very efficient when the power is on but not driving a headphone, yet whatever power conservation tech it uses has no tendency to lag when a signal is applied.