Myself and spouse are CO Gold - we booked a ticket together under my name, then a few weeks ago I split the PNR to maximize upgrade chances.

At 72 hours I was upgraded, but spouse wasn't. Originally same reservation, same fare type, booked at same time. CO website shows one R seat left open. I call CO, they say spouse didn't get upgraded because the "time stamp" on the ticket showed mine as being booked earlier and spouse's time stamp is when the reservation was split.

Agent said she cannot view list to tell me if spouse is "next" to get an UG, and would not "force" the UG even though there is an R seat open and we're within the 72 hour window.

Still (12 hours later) one R seat open, four or five open seats in F, and spouse still not upgraded. My question - does anyone know how frequently EUA "sweeps" are made? Since an R class seat is open, IF my spouse is next, presumably the next sweep should cause an upgrade, right?

The answer to your question can be found on a ton of other threads, so try to poke around for a more detailed explanation. The short answer, however, is that EAU's are capacity controlled so a lot of times if there are only a few seats left, they will hold them in the hopes that a revenue passenger will buy up to F. Additionally, if you are still "12 hours later" than "72 hours out" you are well outside the window for OLCI. That's why you can't get on the waitlist; it's only for people who have already checked in for the flight.

As you start traveling more, you'll notice that more and more often CO is holding back the R seats for possible F purchases. That even happens at times with B-ups, as I found out on a recent BOG-IAH flight. Finally, there is a good chance that there are some plats, Y-ups, or B-ups on the flight so that's why the agent can't 'force' you through.

Hopefully some of that makes sense; I refer you to the numerous other threads for more examples and explanation. Good luck with your travels, and I hope you get the UG!

As far as exact times when "sweeps" are made, it seems like they are made at the regular (T-120, -72, -24) times, but again, subject to capacity controls. Almost all of my recent upgrades have cleared at the airport immediately before boarding.