I got an eGo mower with 7.5 amp hr. battery last year, and I love it! Just out of curiosity, would it extend the battery either by charging the battery immediately after you use up a charge, or by waiting until maybe the day before you're next going to use it and THEN recharging the battery?
I do whatever yard work I need to do, then set the battery on the shelf upside down so I know it isn't fully charged. If the battery went red by the time I was done, I do charge it a bit so it isn't sitting close to empty. Then I'll put the battery on the charger, preferably the slow charger, the night before I need it, or maybe the morning of if I'm going to do my work in the evening. If I forget I just drop it on the rapid charger, but I'm so used to the routine I rarely forget.
I have a lot of hobbies that use expensive lithium batteries, from drones to DSLRs to DeWalt and Ego tools, and all of my batteries are behaving like they did when they were new. A couple of my Ego batteries are more than three years old and still run like new.