Comparative studies of mechanical and electrochemical properties of Nafion ยฎ -and sulfonated polyetheretherketone polymer-type membranes are carried out under severe fuel cell conditions required by industrials, within stationary and cycling electric load profiles. These membranes are proposed to be used in PEM between 70 and 90 โข C as fluorinated or non-fluorinated baseline membranes, respectively. Thus, thought the performance of both membranes remains suitable, Nafion ยฎ backbone brought better mechanical properties and higher electrochemical stabilities than sulfonated polyetheretherketone backbone. The performance stability and the mechanical strength of the membrane-electrode assembly were shown to be influenced by several intrinsic properties of the membrane (e.g., thermal pre-treatment, thickness) and external conditions (fuel cell operating temperature, relative humidity). Finally, a lifetime prediction for membranes under stationary conditions is proposed depending on the operation temperature. At equivalent thicknesses (i.e. 50 m), Nafion ยฎ membranes were estimated able to operate into the 80-90 โข C range while sulfonated polyetheretherketone would be limited into the 70-80 โข C range. This approach brings baseline information about the capability of these types of polymer electrolyte membrane under fuel cell critical operations. Finally, it is revealed as a potential tool for the selection of the most promising advanced polymers for the ensuing research phase.