I had an '87 300E. Put over 100K on it before I sold it to my mechanic. He still has it with 250K and it runs like a dream with the original transmission. The car has had normal maintenance things replaced with the valve seals done once. The transmission had to be resealed but other than that nothing unusual. Normal parts are no more expensive than Toyota or some other ricer.
Anziani
'97 CL500 150K