Found this statistics by BMW drivers on their transmissions and the use of ATF. Quite interesting.
Collecting Statistics on BMW auto transmission and Lifetime ATF
What is your BMW auto transmission maintenance experience? Voters 1286.
Followed BMW Lifetime ATF recommendation, did zero maintenance and auto trans. is fine. 616, 47.90%
Followed BMW Lifetime ATF recommendation, did zero maintenance and auto trans. failed. 151, 11.74%
Did an ATF drain/refill w/ BMW specified ATF fluid and auto trans. is fine. 215, 16.72%
Did an ATF drain/refill w/ BMW specified ATF fluid and auto trans. failed. 50, 3.89%
Did an ATF drain/refill w/ non-BMW ATF and auto trans is fine. 238, 18.51%
Did an ATF drain/refill w/ non-BMW ATF and auto trans failed. 16, 1.24%
The most interesting numbers above is that if you do nothing and treat ATF as life time fluid, 151 out of 767 cases (=151+ 616) result in failed transmissions, nearly 20% failure rate. This is a very high failure rate. On the other hand, if you do ATF changes with or without BMW ATF, the failure rate is 13%, a drop of 7%, which is statistically significant.
Finally, if you do ATF changes with BMW fluid, the failure rate is 50 out of 265, nearly 20%, similar to the case of doing nothing. Why? Dealer-maintained vehicles? On the other hand, if you do ATF changes with non-BMW ATF, only 16 out of 254 failed, only 6.4% failure rate.
So much for the BMW fluid, or any maker branded fluid, if similar statistics hold. Based on the above statistics, I assume that the last group, who are daring to trust the spec, not the brand name, are probably more technical savvy and take care of their cars better.
This survey is not perfect because it does not distinguish how often ATF is changed. Still, doing nothing or following BMW to teeth are the worst off groups. Is it true that if one follows MB to the teeth, he or she may not be that much better off as perceived?