I always ask if I’ve cleared first. If they say I haven’t, I politely ask if they would please check if there’s OY space. I tell them I know in a perfect world RUC’s are supposed to clear automatically, but I’ve had several that didn’t clear automatically even though space opened. I’ve always had very positive feedback from agents with this approach and they say they’re happy to check.

Even when not dealing with a RUC/GUC, I have seen the buy-up offer disappear at some point 1-3 days out from travel. When that happens, the available seats in F are grayed out on the seat map.

I think the entire exercise is to train folks to buy the upgrade when it is offered. Wait any longer, and it may well disappear.

And I would not be shocked to learn that the time that it disappears is variable depending on some secret profile they have developed on each passenger and his/her propensity to buy the upgrade, just like I suspect that the price they offer me to buy-up into F might be different from that offered to someone else.

The entire RUC/GUC process is a royal pain, but I don't think it has any direct relationship to the buy-up process. In general, though, if I am competing for an upgrade using a RUC/GUC, then I hope the upgrade offer disappears for everyone, leaving more seats and thereby increasing chances that the upgrade will clear at the gate.

What remains unclear to me to this date is whether there is any disadvantage to having both the complimentary upgrade and the RUC requested simultaneously. I have heard different answers on this, so I am not sure that anyone knows.