A couple of data points.
Monday 4/17, was #14/83 for zero available seats on a 2:15 SLC-ATL. However, after taking VDB and moving to the 5:15 flight, I was #4/15 for five available seats and cleared about 40 minutes before departure. After boarding I realized the 757 hadn't been refurbished, no old seats and no personal video. I didn't realize they had 757's that hadn't been refurbed; but it did make me wonder if that was part of the reason the 2:15 flight was oversold and the 5:15 was able to clear 25 or so standby passengers.
Thursday 4/20, RUC applied to ATL-SEA, cleared into the only available FC seat about 75 minutes before scheduled departure.