For the price of a clay bar I replace once a year when I do my car in the spring. Gotta keep Mike and his friends in business!
I just don't like using a used claybar. No telling if my son has used it too and dropped it. When I have a new one I know what I'm using.
It sounds like you need to get a Porter Cable buffer so your arms don't get so sore. In 9 hours you can probably wax/polish your car 3 times with a PC (that's allowing time for the polish to dry).
Scratch X is awesome stuff, got a ton of scratches out of my wifes 04 Mercedes. The car looked new when I finished it.
Good luck with your detailing and your spouse, I can identify with that. I do her car too so she can't say I'm spending too much time on "my" car.