Intuition about language learning, however, tells us that with enough language exposure a learner learns virtually all there is to know about any particular word; after the word reaches its adult maturity, subsequent encounters of natural readings do little to further change the knowledge of that word.
if word maturity were tracking something similar to real word knowledge, one would expect the word maturity for most words to plateau over time, and subsequently not change significantly, no matter how sophisticated the reference model becomes.