gmookher said:
my theory, and i cant say I have proven it yet as I have about 90k of hard driven miles, but i suspect the wrong coolant may accelerate head gasket life, just my theory but I am far from a mechanic
That's exactly the kind of "opinion" that adds to all of the old wives tales floating around about coolants.
Coolant is coolant. In an ancient aluminum motor with composite gaskets all that matters is having the proper heat and lubrication properties, not being mixed with a bunch of minerals that will deposit and insulate or clog the cooling system and changing it before it reaches a pH that will eat away at what it touches.
Hint: no coolant is lifetime. Dex was sued over this claim.
Use the damn test strips and do you maintenance. It's not hard, it's not guessing, it's not assuming. It's high school level science class.
Want to argue over which one lasts longer? Go for it. But I sure as hell don't care. They are all good enough to last a couple of years and that's plenty enough for me to feel like I got my money out of them.