Good question and would love to know. I am still on a waitlist for late April for my return DPS-SIN-FRA-JFK. It was scheduled to expire on April 4 but the agent just extended my reservation on the Saver award waitlist to April 11th. For my outbound I booked and have confirmed 2 F Standard awards at 331,500.
I would love to know if they will release these seats and how/when do they make those decisions. I have called a few times and it seems like the agent has been working with me and has sincerely made efforts to expedite the release through the supervisor. I wonder if it helps that I have flown on SQ around 8-10 times over the past 10 years in F and J (both revenue and award).