Based on my limited experience, I'm a bit surprised you didn't upgrade 5 days out as a 75K with an empty F cabin. I would add as well that if you're based somewhere where there are empty F cabins (i.e., not SEA, ANC, or PDX), there's generally not much point in buying the more expensive instant upgrade fare. If anything, it seems to mess up the upgrade processing.

I have to say AS's inventory and revenue management of its F cabin is total amateur hour. They really just don't seem to have any idea how to manage those seats, either for sale or upgrade.