Seems to me that more and more lately AS holds 2-4 F seats until the last minute. In checking this week for my DCA/PDX return for instance I didn't get upgraded as a gold a day or so out, so I did a quick search on the mobile app to see what seats available up until about 3-6 hours before the flight, I noticed the price increased to about $1100 one way and then the upgrades were processed, and I got my upgrade.