The delay of a circuit degrades due to NBTI affects. The accuracy of existing predictive aging models depends on input signal probabilities that may vary during the circuit's life span. In order to periodically test whether the circuit has aged more than predicted critical paths must be tested periodically and this requires a pin to pin aging model to preserve the sensitivity coefficients of the process parameters. Such a model is proposed and a compact test set is derived for the critical paths at each year. Experimental results show the effectiveness of the proposed method.