To make your inverter battery last longer, first; you must disconnect extra load when not required, load separation is an important factor, second; make use of energy efficient devices, for example, quality low rated LED bulbs instead of CFL (energy saving bulbs) and tungsten filament bulbs, third; invest in quality and properly sized batteries that has good life cycle, fourth; charging the inverter batteries correctly in order to maintain the backup and fifth; take good care of your inverter batteries via keeping the battery terminals corrosion free and rust free.