For the record, I don’t agree with this, but I found the wording really funny.
In his 1905 valedictory address to the Johns Hopkins Hospital, the eminent Canadian physician William Osler expressed his conviction that a man’s best work was done before he was forty years old, and that by age sixty, he should retire. He called the ages between twenty five and forty the “15 golden years of plenty”. Workers between ages forty and sixty were tolerable because they were “merely uncreative”. But after age sixty the average worker was useless and should be put out to pasture.
-Wikipedia and William Osler