I'd understood it differently.

It's clear that refunding an award doesn't extend the validity of points that otherwise would have expired; the question, then, was whether one could still use of the value of already expired/redeemed points, by changing the award (either for a different zone at identical cost, or a more expensive one, topping up with additional points).

In my case, for example: in December 2016, I had a bunch of points that were set to expire, but was just short of an international award I wanted. So, to not lose the points, I cashed in my expiring balance for a domestic business class award, which I'm not even when I will use. So: If it turns out one can change the award certificate (even exchange, or a higher award) without forfeiting points from the original issue that otherwise would have expired, that would be fantastic, and well worth the $150 fee.

Just not sure if it's possible...

UXB - apologies if I misunderstood your question.