Learned the hard way today to check for "Upgrade Requested." I passed the 6-day window for an LAX MR and noticed no upgrades. I called in to discover that I had "declined" the upgrade. Ha! 3/4 immediately cleared. The one that Didn't? ATL-LAX on the 77L... 7 seats left on a Monday evening. Ugh!

Just as a data point: I booked 3 identical trips one after another via Kayak. Before going to Kayak, I made sure that I was logged in on delta.com. The first one (today) everthing cleared at 6 days. The remaining 2 all said "Upgrade Eligible" until I called. What's scary is that a couple of trips that I had previously booked via delta.com also said "Upgrade Eligible" until I called. I don't know if they always said that or if the requests were removed somehow.