I also wonder about the international flights. I have been keeping records for the last few trips. My flights are usually booked about two months out. If the upgrades don't clear at booking, some seem to clear about 1 month out. If they don't clear then, it is usually 2 or 3 days before the flight. My upgrades are always to C. It would be interesting to know if there is a pattern for upgrades from C to F. My final upgrades to C seem to come from seats that someone else upgraded to F. I base this on the fact that the desirable seats on upper deck 747 seem to open up shortly before the flight.