All too often we say of a man doing a good job that he is indispensable. A flattering canard, as so many disillusioned and retired and fired have discovered when the world seems to keep on turning without them. In business, a man can come nearest to indispensability by being dispensable in his current job. How can a man move up to new responsibilities if he is the only one able to handle his present tasks? It matters not how small or large the job you now have, if you have trained no one to do it as well, you're not available; you've made your promotion difficult if not impossible.
Malcolm Forbes