I think the counter shaft sprocket size has a lot to do with chain life.
At 46k miles on the DR I'm about 9k into the 4th chain.
I believe that the smaller sprockets, no matter what method is used to lubricate the chain, shortens the life. I've bounced between 14 and 15, but with many more miles on 14. The rear has been a 43 since the first change.
I've tried to perform a test over the last 8 months or so using a Loobman, but there have been a lot of variables - really, too many to make any factual conclusions.
So far, my DID's (all have been the top DID chains) have lasted between 10 and 15k miles.
I don't have enough miles to compare the differences of changing front sprockets inside of chain changes..if that makes sense. But I would like to understand the physics of how a worn sprocket affects chain life. To me - my thinking - one adapts to the other, always mating as long as they are able.
Without any real basis in fact, I believe that an 'often-lubricated' (meaning more than once a day, automatic or not) chain is more fit than one that is not.
I was hoping to find that 20k mile + range for chain life on my bike, but I don't think I ever will. But...I'll continue to do other tests in the hopes that..............