see if i can make a long story short, and make sense, lead/acid batteries rely on a chemical reaction between the lead plates and acid in order to make electricty, as the lead plates absores the acid you lose chg, thats how they work, when you chg your battery all your doing is seperating the lead and acid to keep he reaction going, allowing the lead to countionulsy "soak up" with acid will shorten your battery life. will no longer be able to get seperation, these batteries are the same as whats in your car, just not near as many amps, so yea you should keep them fully charged for a longer life