Only one data point, but from a flight earlier this week, the waitlisted eupgrade requests were automatically cancelled around T-36 hours so we weren’t on the list at the airport and the credits were returned before the flight. Very annoyed that the waitlisted upgrade requests weren’t carried over to the gate, especially with 4 seats open at T-24 hours on a leisure route where there would be a good chance of clearing, but at least the credits were returned quickly.