I have one 6v Optima that is about 6 years old and another one that is almost 3 years old (bought after they moved production to Mexico).
I swear by these batteries, not at them. For the second year in a row, I left the newer 6v Optima in my truck in an unheated garage in a deep-freeze (unheated) garage in northern New York. About a month ago, we had one day that got above 50. There was still plenty of unmelted snow off the sides of the roads, but the roads were dry. I thought that a drive in the Suburban would be a late winter treat (it had been left for hibernation in early November and had not been driven since late September). Without charging the almost 3 year old Optima, I cranked over the engine and it started after about 10 seconds of cranking (time needed to get enough gas into the carbs).
I'll continue to use 6v Optima batteries in my three 6v trucks until I have a problem.
If these batteries are so bad, why would Hagerty Insurance recently suggest that policy owners use Optima batteries? Especially since Hagerty has an excellent add-on coverage for free tows up to 125 miles (towing a truck with a dead battery costs $$$)?
By the way, if you let an Optima go dead, you must use a non-automatic 6v charger (the one time I did this, my cheap 6v charger would not charge the battery, I used a 5-10 amp 6v charger).
