EcoVent should never need to close every single vent in the house, but even if it did, yes the static pressure in the ducts would rise but what is important is the pressure differential around the blower. If you have a totally 100% blocked filter this will cause the highest pressure differential around the blower that the unit will ever see in it's lifetime and it still shouldn't be the blower that's potentially damaged, it should be the evap coils freezing up or liquid refrigerant making it's way back to the compressor and screwing things up, yes there will be more load on the blower motor but I don't see this damaging it unless it's more like a 100% restriction running at 100% duty cycle for a very long period of time causing the motor to burn up.
Heat. If there's no airflow around the blower (and therefore the blower motor which is usually integrated, then the motor will run hotter. Temperature has an inverse relationship with motor lifetime. The hotter it runs, the sooner it will fail. Even if it never exceeds its maximum rated temperature.
