You boil it down to what I wrote on another site several days ago. When our elders die they take a wealth of information along with them that is gone forever. So when people believe in "never trust anyone over thirty" they are eschewing the wisdom of older people. There is a good reason for the saying, "The wisdom of the ages". It takes a long time to become wise. Ask most people who are in theirs 30's and they will say that they are wiser than they were when they were younger. Ditto 40's and 50's. And I don't know any of my older friends who would want to go back to their teens or twenties IF they couldn't take their present level of knowledge with them. We have a cult of youth in this country, and that isn't a good thing.