There is no extension; however, you can bank them into RCI. You need to call soon though, as than banking window closes in the next few days I believe. You then have two years to use those at any RCI that has availability. But it should be noted there is normally a $90 fee per reservation, but that has been waived the past couple of years, just not guarantees going forward.
PM me if you are past your RCI banking window, I might still be able to help.