Amex currently has a targeted offer for 5000 points after renewing an Amazon Prime membership for $99. Originally, the offer showed an expiration date of 3/2/2018, even though there was mention in the terms of an earlier date. Here's a screenshot of the original offer:
However, a friend told me that the March date had disappeared from her offer entirely, so I went into my account to check. Looks like the same thing happened to me - now the expiration is 1/31/2018, with no mention anywhere of the original date. I'm kind of surprised that Amex would change the terms after I added the offer to my card, although I guess they would claim they were correcting an error (since the 1/31 date was in the fine print, if not the display header).
It's still a good offer, but if you were planning on renewing your Prime membership in February or March, definitely double check your account to make sure the expiration hasn't moved up.