I think a more distinctly virtue ethicist way of putting it is that they don't do slightly bad things because that would condition them to have bad dispositions, or to be bad people, something that is intrinsically disvaluable.
People who avoid doing slightly bad things to prevent instilling unhelpful habits, and to prevent themselves from bringing about future harm are (roughly) global utilitarians.
I'm such a utilitarian, I don't understand the difference. What's a bad person with bad dispositions, if not someone who does bad things?
Age Shall Not Weary Us: Deleterious Effects of Self-Regulation Depletion Are Specific to Younger Adults
Brain areas associated with self-regulation don't mature until the mid-twenties. And apparently, if you compare older and younger people in a standard set-up for detecting ego-depletion, older people are not affected. WEIRD, indeed.
In 2010, there was a study indicating that ego depletion doesn't affect people who don't expect it to (and that one was run on college students). I wonder if part of the effect might be coming from differences in attitudes about effort between older and younger people.