I get about 1700KM out of KMC chain. Each year I use three KMC chains in rotation, swapping them monthly. Together the three do about 5000 KM which is 1 annual oil change. After 1700KM a KMC chain is at about 1% stretch and the sprockets are very concave. In 2 years I do 10,000KM and "use up" a 16 tooth Rohloff rear sprocket and Thorn chainring after turning them round halfway at oil change time. After this, the teeth are teeny sharp points, sometimes snapping right off, and the chains are starting to fall off too regularly.
I ride off-road. - This can make 100 times the difference in chain wear compared to clean road riders.
Since I have the "benefit" of using so many chains I can quickly test the theories of the late Sheldon Brown, and thing he had about fitting the chain on the same (even) teeth. It seemed a good idea, but after carefully filing marks on my sprockets, and after always using chain on the same teeth over a whole season, I can safely declare it made no difference at all to chain stretch, tooth shape or resulting chain slack, compared to the time I dropped the chain on in any "phase" each time I punctured. The odd an even teeth all had the same concave shape and the same wear. This was unexpected, but it makes my life simpler since nowadays I don't bother how I fit my chains.