Good question, and I have been debating this myself on my 328i.
My car just passed 58k miles (93k km) and I have been told that old school maintenance would change the fluids on the transmission about now. I've never kept a car though past 100k miles, so I am wondering whether its a waste of my money....I wonder how much a buyer would give me extra value for (the extra oil changes I have performed) or an auto trans fluid change....difficult decision.
I have a friend who is still on the original auto BMW transmission on his 528i and it has nearly 200k miles !!! (with no maintenance)