I have an EGO mower that is on it's 8th year...Original 7ah battery. StAug needs to be cut high so high torque/larger battery is really not needed. Get self-propelled with headlights for those hot evenings in August
The key to long battery calendar life is to charge full just before use and not after you mow...Let the battery sit at low charge between uses. Also, only mow in late evening so the sun isn't beating down on top of your battery.