I don't really follow the discussion about willpower depletion but seeing this post reminded me that I saw that earlier this year there was a registered replication effort that seems to indicate that ego depletion doesn't exist or is a very small effect.

The paper and some commentary:

http://www.psychologicalscience.org/index.php/publications/rrr-the-ego-depletion-paradigm

And the pop-science article where I first saw mention of it:

http://www.slate.com/articles/health_and_science/cover_story/2016/03/ego_depletion_an_influential_theory_in_psychology_may_have_just_been_debunked.html