I don't agree with your math though.
At the normal rate of buying via GC's with 5-10% off, I'd rarely ever give up the Amex warranty. At 33.3%, things start to look different.
So buy the GCs now, save them to your account, use your Freedom card for the 5ppd for those items this month when the bonus won't be 5ppd on Freedom and next month use your GC balance for all those items that don't need the protection of Amex.
Anyone cashing in now is losing out on on the 5ppd they could have made on Freedom through 12/31/13 or the added protections from Amex, while in 2014 they could be buying
diapers,
wipes,
toilet paper, or anything else that won't benefit from the protection with 33% off until their GC balance runs out.
I keep seeing people buying electronics under $10k and other purchases under $300 and even under $100 and I'm wondering how many ways I can explain this
For those that do get what I'm saying, you can try changing your payment method and the GC amount will be added to your GC balance on your Amazon account.