Originally Posted by Doru

The transmission is not built by the car manufacturer. therefore, one should look up what the transmission manufacturer recommends. BMW has no say in this, owner's manual, or service manual.
If one has a ZF transmission, then you should follow ZF service interval, which is 100,000Km to 120,000Km Max. Check this post where a forum member from Europe serviced his transmission at a ZF facility - post #11. Also detailed info what the service actually is.

This should close the debate. BMW has NO say in this, they didn't build the tranny, they just installed it in the car.
But in the end it's your car, and if your pipe dream about "lifetime fluid" fulfills your needs, than don't change the fluid.