Porterfield R4S are advertised as being rotor friendly. But we gotta realize a harder pad that stopps better will be harder on the rotors.
I looked at my rotors after 40k on them with Porterfield's and they are worn, but not much more than a soft cheap generic pad would wear. Nothing excessive. It's not like it's a Hawk Blue that eats rotors after 4 weekends on the racetrack!
To me a little extra wear for much better stopping and more saftey is worth it!
74 REPU Lawn Green
81 Rx-7 racecar. 12a J-