Orchos Tzadikim (Sha'ar ha'Zechirah DH ha'Esrim v'Arba): Chachmah is strengthened when he reaches old age, more than he understood in his youth. Therefore, when your Chachmah strengthens, begin to contemplate your matters, and then you will understand more than initially. Also increase to seek from every man what you do not know - "mi'Kol Melamedai Hiskalti" (Tehilim 119:99). Do not think, who knows to teach to you something that you did not know in your youth? "Ra'isa Ish Chacham b'Einav