Every expert who taught you will retire. The way to honor that is to know it well enough to teach it.

Knowledge only survives by being handed on, and the handing on has a deadline, because the people holding it are not available forever. Learning something properly is a different thing from being able to do it. The real test is whether you could explain it to somebody who knows nothing.

Take one skill somebody taught you and try teaching it to a person this month. The gaps will surface immediately, which is the useful part of the exercise.