Honestly, just unplug it from the wall whenever it's full charge, and only plug it back in when it's almost out. It's best to let it drain before recharging. This goes for a majority of cellphones and some other portable gadgets as well.
this isn't true with lithium batteries, in fact completely draining lithium batteries can be really really bad for them
it might not be damaging the battery, but leaving it charging usually makes it heat up which isn't good for anything!
also i'm pretty sure the charging process is passive, you plug it in and it charges, the computer can just 'see' that it's charging