I am a SM member for many years and untl this years haven't gotten many upgrades; but since i moved to florida a few months ago i have started getting more of them was wondering if online check-in time had any correlation to whether upgrades were granted.

If i checkin 24 hour before the flight when i have not yet recieved an upgrade and there are 8 first class seats available will i get essentially knocked off the list until i get to the airport and reregister or does it have no influence.

Also how come seats are available in first class but the they awarded at the gate whiel other times i get the upgrade a day or more in advance?

Thanks much.