My understanding is this...
It does not hurt the battery to leave it charging, as long as the charger is functioning properly.
But if the charger is not working right, and lets the battery overcharge, you have a problem
And if the battery protection circuit stops working right, and the battery happens to "get hosed" then you have a problem.
And when you have a problem the battery explodes/catches fire.
I am sure a battery expert will be along in due time, and can clarify these matters.
And more importantly, will correct me if I'm wrong.
