Okay Mike, you make a good point. Now, have you checked the thickness?
Personally, I am much more concerned about front rotor thickness than rear. Also, unless you run it at 140 on the Autobahn, you should have adequate mass for 70 or 80 MPH stops unless the rotor is almost cut into two pieces.
The pad does not reach the very largest diameter of the rotor, so you can tell by looking at that thickness step if they're getting thin without micing them. Depending on the pads you use, these rotors will go beyond a few pad sets before being too thin.