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

Age plays an important role in everyone’s life. Mentality level of every person keeps on growing with the passage of time.There is a certain period in life when our reflexives, energy,working efficiency decreases.This happens at a certain age and its a natural life cycle.To a certain level i wouldn’t agree with this statement.
I still believe replacing all the aged persons with young ones would not be a good abstraction.There are lots of myths regarding aged people that they are senile, have rigid thinking, their learning ability stops,they are depressed,they develop dementia but i believe otherwise.NO doubt young peoples are more energetic and their learning abilities are good enough.If they work under supervision of experienced person they would have a greater chance of enhancing their skills in a far superior way.They can learn to overcome difficulties and handle situations in a better way under experience person. Moreover if you left all aged people out of all field that can led to many problems in society.In my opinion we can get better outcome if youth is combined with experience in this way we can prosper in any field in an effective way.