I keep hearing about the huge problem of a 6V GC battery dying and leaving the TT without power, which obviously can't happen with two 12V batteries.
Yet, I don't read many posts on this forum or any other forum complaining about a 6V GC battery suddenly failing. Do they eventually go bad? Sure, but you get the sense of that by observing they do not hold a charge a long as they did when new, or almost new.
As I've written before, is it possible a 6V GC battery can fail without warning? Yes. Is it probable? No. Is it possible someone could slam into my TT, totaling it, while I'm stopped at a red light? Yes. Is it probable? Probably not, but the odds are certainly greater than a 6V battery failing without notice.