The theory behind not changing neglected automatic transmission oil is that the new oil will have better detergent action, which can loosen gunk and either cause things that aren't leaking to leak or not hold pressure properly, or cause gunk to go places and cause BAD THINGS to happen. But my feeling is that if the transmission fails right after a simple fluid R&R, then it was probably ready to fail anyway.
These transmissions are indeed "lifetime fill" in that you get new fluid with your new transmission, but I believe some years ago BMW updated the definition of "lifetime" to mean 100K miles. Some dealers seem to have missed that memo.
I would change it at half that if I had an autotragic, but my cars are both 3-pedal. And still got the transmission oil changed at ~45K. The wagon, which I bought new, actually got a break-in change at 2500 miles, then another at 45K.