Maybe another point of view. The day that AA implemented their new fees and started really pumping selling F-Class ahead of time, I sent an email to AA CS to mention my confusion on the new website and concern for pumping the sales of F instead of upgrades.
I got the response of:
We are still looking for ways to assist those few members who feel like their opportunities to upgrade have diminished. Typically, these customers purchase their tickets in the last minute, that is, inside the 100-hour window for AAdvantageŽ Executive Platinum customers. Their experience is that at that point other elite members have already taken upgraded seats.
I think this is an incredibly important point. They are looking for ways to help out the high yielding, last minute EXP members. I bet this is a big piece of why we are not seeing as many upgrades clearing at the 100-hour mark.
If they are truly basing it on fare basis or yield, then it will remove the benefit of the timestamp of the request. I'm torn as I do both. I book 4 weeks out lots of times, but I also buy the $1000 RT with 2 days advanced notice and grow frustrated at zero chance of upgrade.