This paper presents an original study aiming at evaluating the drift of susceptibility level of a mixed signal circuit during its lifetime. The paper first addresses the issues linked to the experimental set-up and the recommendations required to extract susceptibility level variations. Then the paper presents the evolution of susceptibility after a standard accelerated aging of various digital and analog blocks. While digital blocks remain insensitive to aging, an analog block such as a voltage-controlled oscillator exhibits a significant reduction of its immunity level.