The ATF fluid can last that long because it is synthetic. But the filter
cannot last that long and so much sediments from clutch plates will simply
overwhelm the filter. Once the filter is clogged, it will simply bypass and
let the saturated ATF with sediments flow through... Like dirt in oil, it
will wear down the engine. In tranny, it will start to wear those electronic
valves and all mechanicals inside the tranny.
I got a BMW with lifetime fill tranny... I drained it at 115,000 miles
because my tranny cannot move anymore... and I looked at the fluid... I
can't believe it... so saturated with sediments and blackish. It cooked my
valve body... so once I had someone rebuild the valve body, tranny is just
like new again.
With regular fluid drain and filter change, tranny should last anywhere from
160,000 miles to up to 290,000 miles depending on how you drive the car...
city will get low end, and majority highway will get high end.