Since we have removed the AdView.destroy() it seems like that causes leakage of active adviews which in turn makes the battery usage of the app go sky high on some Android 4.4 (Nexus 5) devices. People have now reported our app using almost all the battery and I see for myself that the log is full of messages like:
I/Ads (13605): Ad is not visible. Not refreshing ad.
I/Ads (13605): Scheduling ad refresh 60000 milliseconds from now.
So we are getting a bit desperate for a solution here. We don't want to move move our entire ad business elsewhere but this is getting to be a big issue for our app now...