No offence, you can disagree, but I personally ran X12's all last year. I had two 10.5's that lasted the whole season, and the only reason I brought a second was because I thought the rotor had possibly gone soft (it hadn't) due to the extra high temps at the aforementioned race meeting. I'm not saying 115 was what I intended to run (I was usually targeting 90-95), but it didn't have any long lasting effects on the motor's performance. I still have that motor now, and bet just as fast as any others out there.
Never had any problem with rotors, and if anything on the X12's only, the higher temp is fine for getting it to run at it's best. Make it too cool, and you loose performance. Trust me when I say I've had a whole load of experience running that motor, and am pretty sure on how to get the best out of them
I will say I was very sceptical about those motors when I first ran them last year, couldn't get the temps down below 80 without losing a lot of performance. Part of that was speedo setup, and part learning how the motor works best. X12, four dot insert, let it rev, and just ignore the higher temps.
The X12 is simply built differently, and uses different materials compared to most other motors. In some respects, it's a stock motor built like a mod, for want of a better expression!