what brand of battery do you run?

The white cased batterys are all made by Johnson Controls as mentioned,,

The black cased batterys are made by Exide,,

The all go under different names,, by who-ever ...

Since batteries became sealed "maint free"., if a battery is overcharge for a while,, and boils some fluid away,, you can't top them up to keep the plates covered,, and that's gonna shorten battery life..

Back when we filled our own batts, I was taught that 50% of all premature batter failure was due to "improper activation",, meaning the weren't filled right,, main concern was un-even fluid levels, and dilution of the electrolyte in the lesser cells when topping off with distilled water..,, that started a "self-discharge" cycle..

Avg expected life of a lead-acid battery,, 5 - 7 yrs..

cheers..