My friend recently posted a blog post where her company performed a brief analysis of the effects of long term stress on drilled rotors. In other words, they analyzed why drilled rotors exhibit vertical cracking along the holes. While it might be obvious why this happens in "general" terms, they provide a very good "picture" of why it happens (you'll see what I mean).
The brakes they examined are from a c6 z06 corvette that had apparently done too much racing and too little rotor changing when it was time to change pads. I know that from a customer point of view, many are weary of buying drilled rotors for this reason, so this should be an interesting article to read. Just as a warning, this is just one of many projects they undertake, and they are not automotive centric whatsoever (as you will see if you navigate to the other articles). They are home to the worlds 2nd largest scanning electron microscope and routinely scan objects to provide a better picture of how things work, literally.
I've posted this on another forum but I figured you guys (and gals) would really love seeing the intricacies of the the slow failure of drilled brake rotors if not changed when required.http://novacentergirl.blogspot.com/2012/02/large-chamber-sem-views-stress.html