I dont rely on a camera and pictures or Heresay to check tolerances. BMW is in the buisness of making money and saving money, but not for you. Changing plugs @ 50k vs. 100k isnt about preventative maintainence. Its about performance and efficiency.
Without writing a thesis, changing your oil is about what people have done for a long time for reason, not some new-fangled BMW propaganda, and tree hugger's far reaching effects of a quest to save the planet. Its cheap insurance that cuts the wear factor significantly. If BMW took care of everything for you this forum wouldnt exist.