And John N, how about sharing some of that arduously collected data? What's your chain life average and the range?
I measure my chains and change them when they get to 0.75% stretch. For my last 8 chains, I have gotten mileages of 4,223, 3,414, 3,767, 4,218, 3,348, 3,340, 1,859, and 3,142. That 4,218 and 3,348 numbers were SRAM 991, the 4,223 was a Shimano HG73, and the 3,414 was a SRAM 951. The rest were SRAM 771. Others have vastly different experiences and I have no good explanations why. Some change their chains every 1,000 miles and some every 10,000 miles. The differences can probably be attributed to a wide variety of factors, including how often you clean and lube, whether or not you're a masher or spinner, how often you ride in the rain, how many hills you ride, how heavy you and your load are, how dirty your roads are, etc.