^^^ point taken - my wording was not clear, my bad. I was meaning that for a given load *within that output curve* that it can support. As long as it is within the output curve, 100 watts is 100 watts, regardless of RPM.
Once the load exceeds output curve (capability) for the rpm, then yes, it can not produce more power/work without additional RPM.
(thinking aloud) The OP was talking about stress on equipment due to idle speeds, and I read it as he was saying that dumping max volts into the alt causes it to work harder- and that's not the case - yes the field voltage is high but the rpm is low so the power output, which is what generates heat in the alternator, is no greater than a high rpm with low FC voltage. It's the stator that's affected by all this, since that's where magnetism becomes watts. I may have gone outside what he was thinking, but as long as the wattage output is constant, ie, within the output curve, it's actually the same load on the device. Since we're being precise, I'm considering FC temps as negligible since it pales in comparison to stator heat.