I called today about a separate question and while I had an agent on the phone, I asked about an upgrade that had been waitlisted for the past few months since I booked the trip. Since a few of my GUCs had cleared since then, I was worried that a certificate listed for this upgrade may be closed. A few interesting things came out of the call:
1. The agent told me that the upgrade had already cleared (my reservation online didn't reflect this) and updated my reservation accordingly
2. The agent told me that in the future I need not worry about a closed certificate being listed because the person processing the upgrade will pull any open certificate
3. When actually going in to process the upgrade, the agent told me that the certificate number was missing from the request (so the agent who did it in the first place must have done it incorrectly)
I suppose it's possible that the upgrade cleared recently and was in a queue to be processed and the timing of my call was just a coincident, but I'm wondering if the upgrade never would have cleared as listed (given it was missing a certificate number) and I just happened to call in when there was OY availability.