Grates tibi ago, Auspex! (even if you are not a fossil member, your screen name may mean you know Latin
A power-off cycle is not generally enough to refresh the cover on my Touch, but I agree with you: these bugs seem to be fairly random.
As for battery over-consumption or rather misevaluation, it did not happen since my last post. But once, I met my Kobo asking for battery recharge though it had been plugged to the computer for at least 30 minutes rather shortly before.
Maybe a process that keeps working in the background? I noticed the same phenomenon on a Mio PDA in 2006. The cursed Microsoft Activesync kept running all the time, woke up randomly and exhausted the battery.