A larger factor is the brake pad compound. I've seen some racing compound brake pads become concrete on wheels as soon as they get wet. I happened to come across this after cleaning an M3 that had said brake pads on it. He stated that short of going to a wheel refinishing shop, there isn't much that can be done. Obviously different pads leave different results but with that amount of time and pad compound used, I'm betting it's on there for good, unless you get them refinished.
You're on the right track with the SHO. Keep them clean, clayed, and sealed to help extend the life of the entire wheel.