According to ransley :

Sure the manual says its ok to leave it in the charger, thats bs, you
might get 5 yrs of life that way, I have 15 and 18 yr old Makita packs
that work a bit, Heat ruins any cell eventualy as over charging
generates heat

http://www.powerstream.com/tech.html, then check out the "How
to Charge Batteries" should help dispell a lot of myths.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.