All that churning sure seems like a lot of work for such a minor change to the FICO score.
In general, this is something I see online a lot: hand wringing about AAoA. Let's look at that facts: Length of Credit History is only 15% of the FICO score, and length of credit history encompasses more than just age of accounts.
This interview with the FICO guy is a little old, but it is still very enlightening:
Does Closing an Old Credit Card Hurt Your Credit Score?
Hey, if you want to churn, that is between you and American Express, but if it actually makes a worthwhile difference to your credit score, come back and tell us. I'll be more than a little surprised.