I don'thave an issue with replacing worn chains to get better life out of more expensive components like cassette and chainwheels, but I don't trust the chain wear checker gizmos anymore.
I used a park CC2 for a while, but started to get suspicious when I was replacing chains what seemed far too often. Sure enough, when I compared an accurate measurement with a ruler to what the chain wear checker was telling me, I found out it was out by 100%, i.e. it was saying a 0.5% stretched chain was 1%.
And I don't think I'd just got a badly calibrated one, aparrently its an inherent issue with the way these guages measure stretch, by including the natural slack between the rollers and bushings - Sheldon Brown's web page used to have a good explanation of this issue, but it seems to have disappeared!
So, my advice is to still replace at 0.75% wear, but use a ruler to measure this!