1. A method for operating a machine component under stress, the method comprising: determining a probability of failure of the component as a function of N cycles, PoF(N); selecting a time-based acceptable risk limit for the component; selecting an operational profile for the component; converting the time-based acceptable risk limit to a cycle-based acceptable risk limit using the operational profile; comparing the cycle-based acceptable risk limit with the PoF(N) values; and operating the machine component responsive to results of the comparing step.