But this is where it gets tricky. That is, it's not 100% since 100% means it would fail the moment you did this.

Strange you asked 100% because if the CPU lasted say 10 years, 100% of 10 years is 10 years less. That would be unacceptable.

https://www.google.com/#q=cpu%20mtbf%20vs%20temperature opens the book on MTBF vs temperature. In short, higher temp = less lifetime. It doesn't mean you can predict it.
Bob