How do you maintain a modern battery? You no longer have to add water and I don't know of anything to do other than to make sure the terminals are clean. My car batteries normally last me 4 years or so and the battery in my John Deere lasts about 8 years.Why not maintain you battery yourself like people used to do and get the maximum life out of it. A little maintenance goes a long way to save a dollar.
If your battery isn't sealed, take a peek!!