It could just be that you may use those numbers on frequent basis whereas you may only see a certain person rarely. I pay quite a few of my monthly bills on line and each time i do, i have to give my 16 digit debit card number. I also remember; my army number from the late 70s, the numbers of every house i have lived in since childhood, the dates of birth of not only my children, but my 8 grand-children also. Yet if i bump into someone i rarely see in town, i often don't recall their name until much later. I don't really think it has anything to do with ageing. More the level of importance attached to numbers/names and faces.