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

Age is just a number it doesn’t matter how older someone,s. From the topic it is clear that we are thinking out to replace younger people with older people. It is not easy to change someone with no reason just because of the age. It is not possible that younger people are having experience like older are. We cannot replace the total older with younger. Because in working field the much needed demand is to be experienced. If older people are not doing their work properly and younger can do that better than of older then they should be changed.
It is clear that younger people are much active than of older people. In working field you want the active and reliable people we can say that they just want the work at any cost.
In working field we cannot change the whole staff or working people at the same period of time. We required a time in which one by one can make the change.