EUAs are capacity controlled, so just because there are X number of F seats does not mean they are all available for EUA. In fact, many people have seen EUAs much later in the window (at T-1 or T-2 days) or even at the gate (battlefield). As long as your onepass number is on the reservation rest assured you're in line for the upgrade. Don't forget that higher fare plats and all presidential plats will get the EUA before you.