I was fortunate, several years ago, to hear Mr. Nicklaus speak at a Georgia Tech Golf Team function. His son Mike was on the team then.
He talked about several very interesting subjects. He said he practiced his long game(driver, long irons etc.) more than his short game. This is the opposite of what we often hear now.
Also, he said his driver was a big advantage, but when he was hitting the club poorly, or did not have confidence in the driver, he would sometimes tee off with as little as a 5 iron, then work on the driver when he got in. He quite often teed off with his trusty 3 wood. This was from a man who was possibly, the best driver(distance, and length) the game has ever seen.