“In today’s society and organizations, people work increasingly with knowledge, rather than skills. Knowledge and skill differ in a fundamental characteristic — skills change very, very slowly. Knowledge, however, changes itself. It makes itself obsolete, and very rapidly. A knowledge worker becomes obsolescent if he or she does not go back to school every three or four years.
“This not only means that the equipment of learning, of knowledge, of skill, of experience that one acquires early is not sufficient for our present life time and working time. People change over such a long time span. They become different persons with different needs, different abilities, different perspectives, and, therefore, with a need to ‘reinvent’ themselves.’ I quite intentionally use a stronger word than ‘revitalize.’ If you talk of fifty years of working life — and this, I think, is going to be increasingly the norm — you have to reinvent yourself. You have to make something different out of yourself, rather than just find a new supply of energy.”
Peter F. Drucker, The Daily Drucker