johnm,
Question for you:
These samples you are watching, are they in covered containers or open to the air? You probably said, but I don't feel like re-reading 5 pages over again to find out.
I asked because I have many quarts of ATF, Marvel Mys Oil, and others that are years old and are not ambering or thickening at all. They are now just as they were when I bought them. Minus what I've used from the bottles of course.
Joe