"Chains wear out and there is no magic lube that will increase the lifespan of a chain...Chain cleaning is also waste of time and does nothing to increase the lifespan of a chain. ..Just enjoy riding your bike and replace your chain when it's worn out."
I believe there is something to this statement. A guy I ride with replaces his chain around the 4000 mile mark. All he does is lube it to keep it quiet. Runs the same cassette through 3 or 4 chain changes. The outer chain ring where he rides most of the time has never been replaced. This bike is about 14 years old now. He is not a masher, but does weigh around 200lbs. Terrain is relatively flat with a few steep hills along the way.
When riding with him he can't hear the squeaking chain so I have to tell him to lube it when he gets home. He never cleans it, just adds lube. It really baffles me as I replace my chain every 1000-1500 miles. I have yet to replace the cassette or chain ring, but the drive train has only seen 3 full seasons.