Any moral system that tells you to devote 23 hours a day to any one activity isn't so much inapplicable as wrong. Consequential morality at least must incorporate strategy.
As Hitchens would say, born sick, but commanded to be well.
If your morality is telling you to do something it's physically impossible for you to do, tell it that it has been over ruled by reality, and should try again.
One of the criteria moral philosophers use to asses the credibility and power of a moral theory is "applicability". That is, how easy is it for humans to implement a moral rule? For example, a rule exists like "donate 23 hours a day to charity" it would be impossible for humans to fulfill the goal.
This lead me to start thinking about whether we want to be able to to pursue "the moral theoretical truth" should such a truth exist, or if we want to find the most applicable and practical set of rules, such that reasonably intramentaly rational (human) agents could figure out what is best in any given situation.
I feel like this is sort of like a map-territory distinction in a loose way. For example, the best thing to do in situation X might be A. A may be so difficult or require so much sacrifice, that B might be preferable, even if the overall outcome is not as good. This reminds me of how Eliezer says that the map is not the territory, but you can't fold the territory and put it in your pocket.
I'd love to be able to understand this issue a little better. If anyone has any thoughts, ideas or evidence, I'd appreciate hearing them.
Thanks,
Jeremy