This work presents a detailed characterization of commercial E2PROMs performed by means of a new technique that allows non destructive monitoring of cell aging. Such a tech nique is based on accurate time control of the device power supply to stop the programming process, thus freezing the charge injected into the floating gate. Since a characteristic time is measured, the experiments can be performed varying other important parameters (in particular the supply voltage), whose influence on device endurance has been demonstrated. Thp method is also used to monitor the floating gate charging and discharging dynamics exploiting measurements of the drawn current.