All of your cards should have the same Member Since date, and any new account should also have that date. Closing a credit card to open one which is more useful should not change the reported age of the accounts.
Oh yes, indeed! I completely forgot that new Amex's share the same benefit as old Amex's.
Hmm, that still leaves me with the predicament of bringing my total personal+biz credit cards down to 4 (from 7). It's difficult when you factor in the Biz cards.
