I haven't been upgraded in months, though 80%-90% of the time in the last 6 months I have been flying in J with no F, or in F.

My last upgrade was mid-flight when I got to chatting with the ISM for longer than I normally do and she bumped me up to J for the remainder of the flight, even though I already had 3 seats to myself in Y. Nothing was wrong with my seat, I guess she just took pity on me...

The mid-flight op-up was a first for me.. apparently it's not too late for an op-up even after the doors are closed..