...otherwise, and if you are to abdicate morality from economic decisions, even if you're able to prove that decisions along different time preferences have consistent outcomes - the question becomes why is a long life better than a short one.

Our laws (old law) seems to preserve the same thing as the correct allocation of capital.

And as euclid taught us in his first axiom, things which are equal to the same thing are equal to each other. And so if economics and ethics are both equal to long time preference - then they are equal to and complimentary each other.