Yes engine compnents do eventually wear out, some quicker than others. Ive been running very large vehicle fleets over the years years including 8000 company cars at one point, and more recently a very large fleet of vehicles of all shapes and sizes operating in desert countries in very tough conditions. We had just about every bizzare vehicle failure imaginable but never a cam chain. The tensioner (if it has one) is often hydraulic and never wears but after many miles of punishment I expect the chain can become noisy along with the rest of the engine, but that tends to be sprocket wear. The MB engine is very well made and if yoiu get a chance to listen to an old Merc Taxi with a petrol engine and 250K miles it will be amazingly quiet.