I must be lucky I get thousands of miles out of a chain. I don’t use a ruler I just pull the chain if it stretches too far off the ring I change it. Or if shifting becomes crummy. I use White Lightning dry wax chain lube. Sometimes I will put degreasers on the chain and power wash it. I know you are supposedly not to power wash a bike but I have done this for years and never ruined anything. But I’m careful with the spray at the BB and other bearings.