Thanks folks. Nice vid, Kirk. I'll do some in-depth testing using that info. The guy at the Interstate (expensive) Battery Center near me said that if I've been only charging with alternator, then to put them on a low amp desulfanator charger for a day or so. Said they were too low voltage to load test (13.3vdc on converter, 12.2 when no load and off charger). The general din I'm hearing is 3-7 years on wet cell and 4-10 on AGM but testing in the ways heard here is in order. And Kirk, I remember when we sold garden tractor batteries at Sears along with the container of acid. And since we dry camp very little, will most likely avoid the expense of Trojan or pair of the 6 volt config.