Concealed Birth of the Imam of the Time عليه السلام was not an extraordinary event

If it is said: Your claim of the long life of your Patron [Imam Mahdi عليه السلام] is extraordinary, as according to you, he remains a man of complete intelligence, strength and youthful looks, because he is, according to you, at this time in 447 A.H., a hundred and ninety-seven years old, as his birth was in 256 A.H.