I had an '86 528e. 255,000 when I bought it, on a just-rebuilt engine. Almost 300K when I sold it. I'm sure the transmission was rebuilt at some point in the car's life, but the car looked sharp as new, and drove the same way (aside from minor creaks, etc. that surface with age).
BMW's on the whole probably last longer than any other car, excepting perhaps Mercedes diesels.