I found that better heat shielding between the PSRU and exhaust pipe improved damper life. The last set I changed had developed only minimal flat spots. Prior to having the batch manufactured I would rotate the dampers 180 degrees opposite the flat spots at annual. This seems to allow the existing flat spots to return back to a more normal condition but likely had some permanent compression.While it is true that rubber spring elements waste a fraction of the spring energy stored and released on each cycle, they can be designed to last thousands of hours with decent airflow over them. Evidence is engine mounts on things like, cars, trucks, and airplanes and giubos used as universal joints in many automotive powertrains. These gadgets are doing the same thing - deflecting to new equilibrium position under mean torque and then vibrating while isolating the engine vibration.
Rubber springs are poor thermal conductors, which can make the task vexing. One approach that greatly extends part life is simply to use elastomers compounded to stand higher temperatures while maintaining modest temperatures with decent airflow over them.