Thanks for the advice. I'll try midweek when I have the option.

RichardInSF: I fly through SFO all the time, but these days rarely manage to get upgraded out of there. How far in advance do you need to book? Any specific times that you fly?

I don't see FF privileges as a perk on United: they're the only thing that makes United's overall offering competitive with other International airlines. If I can't use them I am better off flying on a better airline.