chris, lead acid batteries last longest when kept fully charged, so the best thing to do is leave them on a float charger anytime it's not in use, if you can determine the charge state of the battery it's best to turn the charger off once it's full and then just periodically turn it on to top it off if it's sitting idle for a long period of time. Car batteries for example are constantly float charged by the alternator anytime the engine is running, though more modern cars may stop float charging if the car is running for long period of time as it's not a good idea to continously charge a completly full battery or gasing occurs.