just skimmed through this.. but imho - far too much effort for very little gain. An old/weak/dying battery is going to get replaced in my vehicles. Period. I don't have the time, energy, or money to waste on testing something that simply just needs replacing, and/or could cost me even more down the road by killing my alternator.
I live out in the country - running to the parts store is not a couple minute thing here.. 30 mins one way to get to the nearest. I NEED my vehicle to be reliable and ready to go at a moments notice, not screwing around with chargers and wasting time/energy with testing that is only going to tell me what I already know - the battery needs replacing.
To each their own, and if doing all this makes you happy, then by all means, feel free. But for the majority of us, it is neither frugal, nor expedient to bother with it.
Batteries have a lifespan, and where you are located - geographically - will affect that lifespan. I will spend the $80-85 on a quality battery when I need to, and have the confidence that my vehicle wont leave me stranded somewhere.