LOL. 18,000 service intervals weren't introduced because someone eliminated oil getting dirty and contaminated with use, they were driven largely by manufacturers wanting to bring down the 'on paper' cost of servicing to fleets over contract periods.
But in order to do that, they had to work with oil companies to develop suitable oils. BMW for example have used longlife servicing for more than 15 years. Where are all the dead BMW's that barely limped past 100k miles?