The charger is likely the most important component in the life of your batteries. If you never go below about 50% capacity and you a GOOD multi-stage charger you are doing everything there is to do. Of course never allowing the plates to be exposed and using distilled water only is also critical to the life of the battery. You will hear about adding mineral oil but it's not necessary (just keep adding water) and other additives are mostly snake oil as well. Over time the batteries can get some internal built up so an equalization charge (your good battery charger should have this capability) once a year or so will also added some additional service life.