Just a report on an extension:

I tried a month before expiration and was told "I suggest reaching out in November, three days before your expiration date, so we can maximize the extension."

I tried a day before and they said "Please contact us again once they expire, and we'll see what we can do to help. Unfortunately, I don't have the ability to extend the voucher validity at this time."

I tried again today and he actually asked for my account info so it sounded promising, but then he said he could not because "it is only valid within 12 months", then I said I know it's 12mo, that's why I was asking for an extension, then he said he couldn't extend it because I have "already used some of those vouchers", and "you already have redeemed some of your Food and Beverage Rewards"

I tried again just now (10pm before expiration). This time they forwarded me to the Rewards Dept. Then they spoke to a supervisor and finally approved my extension. I had one CSU they extended 6mo and 2 F&B they extended a year. I hope to use the CSU in december for a 5 night stay in munich at a HI.

I'm platinum but earned using promos with only 10 night stays. I've only had 9 nights this year. Maybe thats a factor.