The easiest way for me to know what I can and can not use is to figure out the UY that my trip will fall. Then I know I can "pay" for my trip with banked points from the UY prior to travel, points for UY of travel, and borrow points from the UY after travel.
So, for a June 2012 trip, it takes place in your Aug 2011 UY. You can use banked 2010, 2011, and borrowed 2012 points for that trip.
When you call does not matter, only when you will be traveling.