I can tell you all, (as a now retired Auto Transmission Specialist), and this was categorically proven on fleet vehicles ....................
If you don't change the Fluid and Filter, when the Trans gets to 100,000 miles + it's on borrowed time ........................
Before everyone yells at me (and Jeff fires me)
, no not every car, too many variables, but yes as a general rule :P
Now ................. Change Fluid and Filters at 80,000 mile intervals, (do the Connector Plug too), and I have seen many 722.6 Trans go to 300,000 plus, and even on 2 of them (W639 Vito Minibuses), they only got stripped and overhauled due to a Converter Lock Up shudder problem, Clutches etc were still in very good order, and only one of the pair needed a planetary gear-set as one thrust washer was in bits in the pan and she was slightly noisy on over run in 1st gear
All Oils and Filters on any vehicle should be done regularly, I don't care what Mercedes, BMW etc etc etc say, there is no such thing as "Lifetime" Oil, a Manufacturers idea of "lifetime" is 100,000 miles, or when their Warranty expires
HTH, Cheers Dave