i dont think it is an issue with manual trans, in the 60,s and 70,s we never ever changed manual gearbox oil, and not a real lot has changed in there design in that time ( yes i know they are improved for a whole host of reasons but the statement stands) even an auto trans from the 70,s maybe got an oil change once in the cars life time
however with the hi tech nature of todays autos and all the electronics and electro magnet solenoids etc, im of the opinion that changing the oil at regular intervals is a smart move
my personal experience with my 05 3.0d is that the fluid change at about 70,000 km dramatically helped / cured the dreaded lurch, along with software up grade
i,m also of the opinion that in stating that the oil is designed for the life time of the vehicle is also true in the eyes of BMW as i dont believe they care a toss after the vehicle has done 100,000 km or once the wty has expired.
they want you to trade it in and buy a new one.
its just us who want better value for our dollar that insist in running them for years, and in my view changing all fluids regularly can't hurt