| Agreed. But, I didn't mean to imply that the heat had to be excessive to damage iron rotors. Just repeated thermal cycling at temperatures developed during normal track and street conditions (age if you wish,) will set-up high material stresses, particularly around discontinuities like the cross-drilled vent holes. A brittle material will have a tendency to develop cracks whereas a ductile material will yield locally. So just inspect them.
BTW, don't take my comments to be derogatory, just cautionary. I think that ductile iron rotors are the single best change that you can make to improve your brakes. | 
Shazaam!
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