My last three flights as a gold I have not been able to move myself up at 12:01 three days before or even 48 or 24 hour mark. Oddly in all three cases I got an F upgrade when I checked in so never tried Premium at the last minute. But as with the OP I have always been able to upgrade myself at the T-3 days at 12:01am, or at the very least T-3 and now not at all. What has changed? The policy on the website seems to say it’s still a perk.