Laffer Curves across the map

Surely every field, every discipline, every profession will, at some point, demonstrate some corollary to the Laffer Curve. Art Laffer's famous napkin sketch (basically a frowny face) doodled for President Reagan describing how there is a tax rate above which revenue decreases rather than increases, i.e., becomes counterproductive—I assume—applies broadly, across the map. In my own area of homiletics, one often hears the objection that a sermon exceeding the attention span of most hearers will "tax" them overmuch, and instead of inspiring them will make them restless. What about your field, your experience, your congregation, your constituency?

Lord willing, I hope my sermon this morning does not run too long. I would much rather be greeted with smiles.