Unfortunately, these upgrades are capacity-controlled, and even if there's a business or first-class seat for sale, you won't always be able to grab it with an upgrade. It's fairly simple to identify flights with upgrade seats available, however, so with a bit of patience you can usually find something that will work.
One major downside to these upgrade certificates is that they expire on January 31 the year after they were issued. So if you qualified for 2015 status based on flights you took in 2014, your upgrades expire at the end of the month. There is one saving grace here, however — United is currently allowing elites who re-qualified for 1K or GS status to extend the expiration of two Global Premier Upgrades, assigning a new expiration date of April 30, 2016. That gives you three more months to use your upgrades, or give them away to a fellow TPG reader in need.
To extend your upgrades, call the MileagePlus Service Center at 800-421-4655. There's a chance you may be able to recover your upgrades even after they expire, but I'd suggest contacting MileagePlus before January 31 just to be sure. After your GPUs are extended, they'll automatically be pulled first (ahead of upgrades expiring in 2017) when you apply them to a reservation.
Did you call United to extend your Global Premier Upgrades?
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