I welcome criticism of my new personal favorite population axiology:

The value of a world-history that extends the current world-history is the average welfare of every life after the present moment. For people who live before and after the current moment, we need to evaluate the welfare of the portion of their life after the current moment. The welfare of a person's life is allowed to vary nonlinearly with the number of years the person lives a certain kind of life, and it's allowed to depend on whether the person's experiences are veridical.

This axiology implies that it's important to ensure that the future will contain many people who have better lives than us; it's consistent with preferring to extend someone's life by N years rather than creating a new life that lasts N years. It's immune to Parfit's Repugnant Conclusion, but doesn't automatically fall prey to the opposite of the Repugnant Conclusion. It implies that our decisions should not depend on whether the past contained a large, prosperous civilization.

There are straightforward modifications for dealing with general relativity and splitting and merging people.

The one flaw is that it's temporally consistent: If future generations average the welfare of lives after their "present moments", they will make decisions we disapprove of.