There is an age after which one’s efficiency decreases. Should young people in the working fields replace all the old people?

In a human life cycle, first stage is childhood when he start his learning. Then he gains more strength mentally and physical and becomes young, energetic and enthusiastic. He feels he can conquer the world by his efforts. He gives his best and achieves his goals and objectives. He performs his duties efficiently and effectively. But gradually, with the passage of time, he begins to feel himself little bit feeble physically. His efficiency slowly diminishes. But this is the age when he becomes golden asset for an organization. Through his practices and experiences further mistakes and misunderstandings can be prevented. Although they are no more energetic and cannot work in fields very well as compared to young people but their suggestions, advises and forecasts should be taken into account which may contribute to well-being and progress of an organization.