[malfist]

I'm not saying a motor turned off will consume the same power as a motor turned on, that's foolish.

Back pressure doesn't impact the load of a fan motor, at least not as the scale we see in HVACs, we're not making vacuum chambers.

[foobarian]

Maybe our disconnect is that we're talking about two different things, one being the rated design point of the blower system, which is presumably constant (though newer systems seem to be more sophisticated), and the other being the exact load and power consumption that depends on backpressure. A higher backpressure will certainly increase the motor power consumption on a classic induction motor - if not by 100% then by some non-zero amount.

Anyway at the end of the day I agree with the original characterization of wear and tear - motor and blower will probably outlast most other components. In the case of the one I mentioned this seemed to be true. You just may end up paying a little more for the electricity to run it.