This clip has been around for a while, but first came to my attention over the weekend. It's John Madden -- hearing that voice brings back so many memories, like smelling freshly baked chocolate chip cookies in grandma's kitchen -- talking about attending a clinic as a young coach and hearing Vince Lombardi speak for eight hours on a single play.
Whether or not Lombardi truly talked for eight hours is beside the point here, but it brings up an interesting point on mastery of your subject. Personally, I'm not sure I could give an 8-hour talk summarizing my entire life, let alone a single topic as focused as one single play.