About battery life...

[Spiritix]

Hello, people! I'm sorry if this is the wrong place to post this, but I figured it was relevant enough.
Another fellow mentor and I have been wondering how we should be charging our batteries so that they'll last. I know batteries aren't meant to last forever, but we've had batteries that die sooner than others.
Last season during a regional competition, I visited another team that we're friendly with so that we could check and see if our battery was acting up, or if it was just the charger. Our chargers will say that a battery is half-charged on some batteries, but it'll stay like that, never increasing. In this case it was the battery, and she recommended that we keep batteries on a low-amp charge over the period we aren't using them actively. While that does make sense (keeps the chemicals active) is it practical? I know other kinds of batteries will over-charge and be damaged that way. So what do you guys think?