Three sets of 10 motorettes were characterized along aging. Thermal aging consisted of isotherms at 240°C. Electrical aging consisted of the application of an AC voltage just above the Partial Discharge Inception Voltage (PDIV). Aging sequence was a series of 6 cycles of 72 hours. In between aging cycles, the evolution of PDIV and Insulation Resistance on Coil-Coil and Coil-Ground configurations were monitored. Polarisation Index provided by the ratio of measured resistance after 10 min and 1 min were calculated. As concerns thermal aging, PDIV decrease was of 10 to 22%. This decrease occurred mainly after the first aging. Electrical aging under partial discharge activity can be revealed by a significant increase of the Polarisation Index. Electrical aging led to 90% failure during the third aging cycle with typical PD-free EIS while none of the motorettes with strengthened EIS were affected during six cycles. PD analysis revealed with the strengthened paper a specific behaviour consisting in a discontinuous regime of discharges.