6V batteries in Ontario

6V golf cart batteries do have heavier plates, and probably are less prone to shorts, but the surety of a 2X6V bank failure when a cell does fail, are 100%, whereas a cell failure in one paralleled 12V battery may not bring the entire bank down. I had one 12V deep cycle battery fail in a paralleled setup, and the other battery managed the load, but for shorter periods after charging them by driving. I figured one had failed hard or was failing because of dimmer lights after a few hours of discharge in the evening, and later determined which one had failed. After that trip, I decided to replace both batteries with brand new, rather than risk running with one new, one older. I think it makes sense to replace both batteries when one fails in a 12V paralleled setup, whether they're both pooched or not. Like when one headlamp goes, the other one won't be far behind. Maybe not as important in a 2X6V setup, due to the more rugged nature of 6V batteries, I'm not sure.