I have my information from German c't magazine. But I found an English source that also provides some experimental data on battery aging: Note figure one on this page: <http://www.batteryuniversity.com/parttwo-34.htm> > The speed by which lithium-ion ages is governed by temperature and > state-of-charge. So, as I said before, yes, the cycles are an issue. But from what I read and (sadly) personal experience, the permanent charging stresses the battery more. )c: Björn