So much of this is just stuff that sounds nice until you think about it, codifying ageism and blocking older people from political life is unjust and undemocratic.
This has nothing to do with age and everything with ability. A test of mental abilities would be fairer but then a lot more politicians than the old ones would disqualify.
A test of mental abilities has a long history of being used to exclude ideological or ethnographic opponents of the majority. For example what language would the test even be in?
The problem there is, who makes the test? How do you avoid a regulatory capture type scenario where one party (you know which one) games the system so that the elder statesmen on the other side of the aisle are the only ones who lose their seats?