Here are some data....shows what you would expect, overall the house will win. This is for my 3 vehicles. Note I have almost 3 years left to make up that last bit which I have a reasonable chance of doing based on my use/history. Also note I have re-upped on the 2 replacements so those go longer than shown - not sure how they can tell if which tire that works for.....
Ok, I've made money! Got my third payout on my DT certs today. Continental ECS02s on my Sportwagen that I bought last spring. Had a nail they fixed a few mos. ago that started leaking, new tire ordered to replace it today. So that's 3 tires replaced in the last few years on my VWs and the math puts me ahead now of what I paid for the certs and of course at my rate it's likely I'll get one more before it's over.