I normally fly UA from ORD to NRT to BKK. I normally only upgrade the longest leg, going or comming and do it at the counter when I get to the gate.The last time I asked to upgrade it was from NRT to ORD. Like I said I can't remember what I paid for the upgrade. For now on when I book economy I will also check the first class fare before I go to see what the price difference is. I was just curious if this practice is used often and what were peoples experiences with it. Not necessarily looking at my individual case but how it worked for other people. Just curious.