When do they pull GUCs
 

I have a couple of reservations which in which I used my GUCs. In one case the space is on a KLM marketed and operated flight (booked in full Y) next week, and the other reservation is a discounted DL marketed and operated flight in November. When I go to my SkyMiles profile it is showing that I have not used/applied any of the GUCs. I would have thought they pull the certificates when they do the ticketing which does show me in DeltaOne.

The reservation may show you in D1, but I doubt the ticket has been reissued. They've been waiting on ticketing lately for some reason.

GUC
 

Does that imply there is any uncertainty about the upgrade. The seat is assigned in delta one. If they might put me back in economy I would just buy a business class ticket. But I would want to do it now so I can get a discounted fare.

You’ll be fine, but I would call if the ticket isn’t reissued 3 days before the flight.

No doubt on upgrade. You've been upgraded. The ticket just hasn't been reissued. (This is when the GUC will show closed) The ticket can be reissued at anytime prior to travel for DL operated flights. You wont be able to checkin till it's reissued, but it can be reissued at airport.

Personally I would call and get reissued as you have segments on KLM metal. These flights can have issues in KLs system if the ticket isnt reissued within 24 hours. (Doesn't mean it will, but it can)

The main reason they've gone to delaying reissuing, the GUC isnt attached to reservation till ticket is reissued. This means if you cancel reservation or decide to cancel, the GUC isn't stuck with the ticket. No issue for DL metal, but this can cause issue with partner metal, and they're supposed to reissue still while on phone if upgrade partner metal.

Have similar situation with 2 GUCs I used to get upgraded on a flight in February and am fully confident you'll be fine.

My return is actually after the date they expire, which should have been an issue, but I still got the confirmed seats for both legs.. So either the agent was nice, or I will get questions at some point...
Then again, DL will indeed not revoke the upgrades, they'll just ask me to give a new GUC, but the longer I can wait to activate my choice benefits the better.

Booked flights in April for flights now, confirmed at booking but never got reticketed until I called after not being able to checkin. Didn’t take too long but worked out ok!