Reviving old batteries?

I wish I knew if the mfg that made the batteries in my 04 Dodge 2500 diesel did something different! I bought my truck in October of 03.....and it still has the original batteries! 98K miles, and spins over good as new. I have wondered if it has to do with the way I use the truck? When it starts up and pulls out of the garage, it is on the road for 300 miles before I stop. I rarely use it for short trips or around town stuff. To the point of the OP's question, I met a guy a few years ago that had gotten into refurbing dead batteries. He bought a bunch of stuff from a snake oil salesman to do it with. I saw him again a year or so later, and asked how the battery thing as working out. He said it was a waste of time to try and do it as a side business gig, as more of the batteries failed again soon after the rework than ones that did well.