Admittedly, it is hard to predict a given battery brand's longevity...especially since said brand MAY have changed their specs either in a good or bad direction. There are many brands, but only a few manufacturers.
Since I draw mostly from my own 29 year Viper experiences, I have learned to stagger the battery changes amongst the Vipers so that I am not too heavily invested in a given run of batteries at a set point in time.
Faithful use of battery float (smart) tenders and smart chargers certainly extends battery life...as does "sleep mode" on Gen Iii's, IV's, and V's. I always make sure that I am using the correct unit for the type of battery in the cars.
Though I am a big fan of the AGM type, I have found that charging them from a low charge state can require different methods as well as close monitoring. It is not as simple as I thought in my younger days.
It seems as though the wicked summer heat across the country is causing a wave of battery failures in stored Vipers...as would be predicted. If one is facing the purchase of a new battery, (and their ever increasing cost), my own advice is to check the date sticker...buying newly produced rather than one on the shelf for several months. Next, check the resting voltage, load test, and cold crank readings at the store before buying...being sure that the battery has not been charged in the last 30 minutes which could give one inflated positive readings. Finally, charge the battery fully BEFORE installing it in a car...then let it sit off charger for 24 hours, and recheck readings. If OK, install battery. If questionable, return to store. All of that said...when in a pinch, do what you have to do !!!