When the tiny pony is a negative thing, many call it Creeping Normalcy [1]. Sounds like the same phenonmenon to me: adjustments that come slowly enough do not get appreciated. Louis CK has a funny bit about it [2].

[1] http://en.wikipedia.org/wiki/Creeping_normalcy

[2] http://www.youtube.com/watch?v=8r1CZTLk-Gk