Assuming they are "flooded cell" batteries rather than one of the sealed types, just check the water level in each cell periodically. I would check every 30 days until I had a feel for how often the water gets depleted, then adjust the frequency accordingly.
The other maintenance is to keep the battery posts clean and free of corrosion. You can buy a spray on solution to help prevent such corrosion. Most any auto parts store should have it.
I agree with DOn. If the case is buldging, it's time to replace it (them). Overcharging, causing excessive heat, leads to the plates shedding their lead paste. That and sulfation will cause those buldges. As for equalization, that only applies to flooded cell batteries, not AGM's. Equalization is a form of controlled overcharging which will help restore a battery and remove sulfation if it is not too extreme.