Many European cars clearly state that their automatic transmissions are filled for life and that replacing the fluid is never required. This is a very bold claim and I believe one that is incorrect!
Transmissions have hundreds of moving parts some of which are friction materials such as clutch discs. All of these parts wear and contaminate the transmission’s fluid. While the fluid may well be designed to handle the heat of the transmission forever, the contamination remains inside.
Recently we had a client with a 2000 BMW X5 whose transmission suddenly started malfunctioning in a serious way. The vehicle had 180,000 kilometers which is not a very high mileage for many vehicles.
To be fair, these particular transmissions do have concerns that will cause premature failures. However routinely renewing the fluid with an automatic transmission flush throughout this vehicle’s life, about every 50,000 kilometers would have added some life to this transmission… if not prevented this early death.
In this case the manufacturer got what it wanted: the sale of another vehicle as our client chose not to repair the vehicle and bought a new one.