drove 12,000 on these brakes

Sounds like your brakes should last some time if you only drive 3000 miles in a year. The brake rotors are not difficult to replace or remove for machining. I personally like replacing them rather than machining, less time involved (no machining) and you have new metal. That'll cost more than machining, I guess, but I like the new metal. I don't know your mechanic but if you think he's hustling you, there are others and a good independent Mazda specialist is the one you need. If you want to find a Mazda specialist, here's our directory link for you: https://repairpal.com/mazda-repair-in-laguna-niguel-california