Well it all depends on lining composition doesn't it. Some of the pad manufactureres now claim that outgassing isn't the problem it used to be. I'm in no position to call BS or not. They all have something to sell though, and this arguement gets heated when it then turns to the question of whether slotted or drilled rotors are better. What I do know is the old Fred Phun book recommended drilling for racing, when running out of other options. Having those discontinuities required constant checking for indications of cracking. They even would drill the drums if needed.