My e90 has nearly done 170k km and I would also like to do a coolant flush. Planning to as soon as i get a gap to look for a diy, or sommer tell the techie to do it.
My e36 was very very dirty when i replaced the radiator, so rather safe than sorry. Car makes dont care much for a car after 150k km is my feeling. I think they will neglect to mention stuff...