Replace with better deep cycle battery (12v or 6v). Any battery is better than the OEM Harris Battery IMO. They should last all night just fine so no need for 3 (Unless you want even more storage).
Two - 6 Volt AGM is best (IMO). But if you have room for 4 then go for it.
I did extensive research on this before I replaced my 2017 Axis batteries (which were only 11 mo old) with Two Full River AGM 6volt. The AGM’s are a little shorter than 6 V lead acid, which allowed them to fit under my step.
See my writeup; Not sure how to attach link here but it was "review of my 6 volt AGM Batteries"
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