Unless the rules have changed, you can transfer current Dec 08 points before December, 2008. In Sept, 2007, we received a transfer of April 08 UY points.
You should note, however, that you cannot borrow transferred points, so if you transfer Dec 08 UY points, they cannot be used for a stay before Dec 08.
In May 2005 I received a transfer of Aug. 2005 points into my account. They could not be used for a stay until after Aug. 2005, although a reservation could be made before that time.