This has been discussed several times but I thought of starting a thread to share our experience with finding availability several weeks/months ahead of time.

I recently upgraded 2 passengers from X to I on the same flight in 3 months time (X being one way flex fare). I did each passenger separately.

Availability was showing I9 prior and remained I9 after the first upgrade was processed.
But when I completed the second transaction it became I0!

Something tells me they are restricting upgrades to 2 seats a flight. Could this possible? This is very similar to RJ.