Each year when I write my final, I learn something new about the material. I teach a course which emphasizes problem solving and some of the basic tools in the field. Every year, there are new innovations in practice, and you can use the basic tools to analyze them. And each year I realize how important the basic tools are, relative to teaching the new buzzwords. Over time, I have taught less and less material, but taught the material I did cover better and better.
The best email to get is from a recent grad who says “The material in your course really prepared me for dealing with new innovations in practice” Such emails don’t come often, but when they do, it really makes it all worthwhile.