Modern charging circuitry could account for this by discharging the battery periodically, but laptops and other consumer-oriented devices generally do not in order to maintain immediate readiness for on-battery use while charging.
==Joseph++
<snip> That makes me wonder if any laptop charge circuits actually do this and/or even shut off charging at some level.
I know that my Lenovo x220's charge light goes out approximately when it reaches a full charge. I usually disconnect the charge once I notice that so I don't know if it is actually disconnecting the charger or if it is only indicating the charging is "complete".
-- Dazed_75 a.k.a. Larry
The spirit of resistance to government is so valuable on certain occasions, that I wish it always to be kept alive. - Thomas Jefferson