Well, it's just pure speculation on my part, but that's what I've noticed lately. Amex puts up a page with "Blah-blah-blah is a Special offer until YYYY-MM-DD"...then BANG!!, on DD or DD+1 we get enlightened with "news". Don't hate me if you apply early, and then it turns out Amex revises their promo to make it a 100,000 point promo!

One recent exception is the Amex Gold MR Rewards card...I don't think anyone saw that one coming; removing any signup benefit from a referral, and up'ing the standard/non-referral welcome points from 15K to 25K. They decided to roll it out in Sep 2013, at the same time that they introduced the current AeroPlus Gold 30K promo. So, there ya go, watch for the Gold MR Rewards promo to get right-sized too, back down to 15K! You can take that to the BANK!!