I think there are two subtly different types of activities to be teased apart here.
In the first: you’re nominally an “expert in X” but most of your time/energy goes, not into X, but into telling other people how they can become good at X.
In the second: you do spend a lot of your time/energy doing X, but your need for X is mainly generated by how you disseminate your expertise about X. In other words, if you were to cease regularly talking about X, your actual need for X would be greatly diminished.