The points you banked from your March 2004 UY will be usable from 3/1/05-2/28/06. You must use all of the banked points during that time period or they expire.
As for borrowing, you can start borrowing from your 2006 UY as soon as the reservation window opens (in your example, you could have started borrowing 2006 points for ressies beginning 3/1/05, which would have put you at 4/1/04 for the 11 month window). Of course, you will want to be sure to use banked points first, then current points, then borrowing. Remember that banking and borrowing are final transactions and cannot be reversed, so just be very detailed in planning these activities.
Good luck!