What your continued use shows us is that high demand hard discharge cycles are what really put the hurt on the life of these batteries, and shallow, slow discharge cycles are, while harder on voltage to recharge fully, what adds longevity to the life and use of a battery.
It makes perfect sense to me... Use in a golf cart with my T-1275 with many deep discharge cycles on the golf course made the battery unfit for use in a golf cart. I still got another 2 years out of it for camping purposes powering light stuff in my TT. What worked it the hardest was my water pump when taking a shower, a 5 amp draw. If I had just run my generator to recharge while taking a shower, I may have still been using the T-1275. Heck, it might even have still been alive a year later.
Thanks for the update... keep checking your shorts on your batteries. Me, I check for battery acid holes burned in to my shorts. I wrecked 2 pair of Levi 550's doing acid dips. None of that happens with my AGM, so it's been a money saver in other ways, my sloppy acid dipping procedures are just no longer an option.