I understand what you are saying. It is ridiculous that BMW is so stubborn about this topic however. Stubborn in regard to fluid-life, stubborn in regard to cost-to-replace, stubborn to not listen to common sense and empirical evidence.
First, the notion of a lifetime-fill on manual transmission fluid begs the question to define 'lifetime'. Four years, ten years, where is the lifetime line drawn.
Second, cost to replace. I have heard some obscene estimates quoted by dealerships (greater than $500 type numbers). Granted, when you go to the dealership, it will/should be more expensive. Dealerships have to maintain massive infrastructures in terms of equipment and HR-related training and processes. The trade-off to this higher cost is the work should be performed perfectly and cleanly. Despite all this, replacing the manual transmission oil is at most a one-hour job - drive the car onto the lift, lift the car, remove plastic under-body panel, remove transmission fill-plug, remove transmission drain-plug, drain fluid, replace drain-plug, pump 2-quarts of new fluid in, replace fill-plug, replace plastic under-body panel, lower car, pull car off lift.
Two quarts of a quality fluid cost at most $25 retail. The only other potential part required is a new fill/drain plug if your old one is not sealing properly (not a bad idea to replace regardless). A new plug is $15 retail (about half that from Tischer). So at most we are talking a $200 job including a $150/hr labor rate.
Next is the stigma using something like Red Line or Royal Purple. I can't speak for RP, but Red Line is one of, if not the most, respected transmission lubricants on the planet. Across the spectrum of cars, Red Line MTL and D4ATF have legions of loyal and satisfied customers. Word-of-mouth aside, there is plenty of empirical evidence collected over the years concerning these lubricants.
So if you put Red Line in your transmission, your transmission warranty is voided. So be it. Though possible, a failure in your manual transmission due to the type of lubrication used (assuming you have the correct type fluid) is remote. Plus, any wear-and-tear item in there is not covered by the warranty anyway.
Personally, I would rather drain and replace every two years than ride on factory fluid for four years only to suffer a malfunction in later years that was caused by riding on the factory oil for so long.
I could go on and on. The coolant 'lifetime' fill is the same thing; no worries on EVER swapping out your engine coolant, it is good for life. Utterly ridiculous. 15,000 mile oil change intervals in a motor that has a nominal operating oil temperature of 240-deg F. Utterly ridiculous. The lifetime rear-differential fluid is perhaps the easiest of the lifetime fluid pills to swallow, but even still, the idea is utterly ridiculous.
I am not sure of the percentage, but I thought I read that the majority of BMWs sold in the United States are leased. Because of this, I have to believe that lifetime to BMW means six years - 4 for new vehicle warranty and 2 for the Certified Pre-Owned warranty. After that - bueno suerte hombre.
If I were in the market for a used BMW that I intended to keep for 8, 9, 10 years, the previous owner would have to prove to me that they did not adhere to BMW's maintenance program but EXCEEDED it in almost every regard.
Rant over. Sorry for the
