My "final word" on the topic of the 722.6 transmission is:
If the transmission fails, it's not neccesarily the fault of the fluid, as "everyone" tends to think. Just because the transmission has (fill in the blank) amount of miles on it, andf it fails, and the fluid was never changed, does not mean the fluid is the fault.
It may be driving habits, or your kid took it out some night and did "hole shots" with it, or some tolerance may have been a little off when it was built, or it got a chip of metal off a gear and it jammed a solenoid (which a fluid change would have had no effect on), and on and on the reasons can go.
Change the oil at 30,000 miles if you'd like, or change it at 300,000 miles. If the thing is destined to fail, it will fail. I've SEEN them (722.6 transmissions) go 300,000 miles without ever being serviced, so I know they CAN do it, if, to a certain extent, you are "lucky".
Sorry if this sounds like a rant.
Glad I got it off my chest anyways.