So much easier and wiser to trust folks like Darren Appleton or Neils Fiejen for knowledgable instruction than some guy named Dr Dave. Just is what it is. Not to say that lesser players can't teach but all things being equal how on earth can Dr Dave know a thing if he's never competed at a high level. There's more to this game than drills, hole reinforcers and slow mo video. No substitute for experience and Dr Dave just about has to be 3rd in this list behind Mark Wilson and Bob Jewett. Age and health are factors but if everyone is say 50 years old and moderately good health I imagine Dr Dave gets run out of the gym.