Excellent points, and particularly interesting real world examples I must say.

I agree with your thoughts on fluid analysis and that, just like in virtually every science, multiple data points are preferred if one is to make any educated guess on the future based on prior results. I think what Blackstone is in reality saying in their assessment is that they need more data points to see what is really going on. And much like you said, an analysis at another relatively short mileage would help answer (somewhat at least) the question as to when some of the particulates are appearing in the fluid; at break in a long time ago or relatively recently.

What I do find interesting is that ZF seems to be implying that since modern fluids are quite stable and have the ability to hold particles in suspension for longer periods of time, that failures caused by fluid changes shouldn't happen... at least up to a point. The question is just what is that point... 80,000km, 100,000km, 120,000km, 100,000 miles or 8 years?

Your heavy equipment example got me thinking. What would be an interesting thing to look at is what other car manufacturers that use the same transmission and fluid recommend. It won't be a perfect comparison, because those manufacturers (Audi, Bentley, Hyundai, Land Rover, Jaguar, Maserati, etc) will all have different software to operate the transmissions differently from BMW, however what would be fascinating to know is what Maserati, for example, thinks in terms of fluid change intervals on a ZF 6HP26 transmission used under their definition of "normal" conditions in a sports car versus Jaguar who might use it in a luxury saloon, versus Land Rover who uses it in a true SUV, versus Hyundai who uses it in their whatever mobiles?