There was a bounceback offer in my rooms in October 2007 (BWV), January 2008 (Pop and AKV), April 2008 (BWV) and May 2008 (BWV). All of the 2008 offers were a stopwatch flyer telling me time was running out. If you don't see a flyer, check the WDW info channel. When it gets to the resort section, it will telll you if there is a current bounceback being offered. Generally it is the last thing they tell you on the resort section before moving into another catagory. Often there is no flyer in the rooms, especially DVC rooms. So watching this info on the TV will help you to know. Once we saw it on the TV we went to the front desk and asked for a flyer. Of course we have yet to ever book this offer as we do better using our AP discount, but luckily we got the 40% discount on our upcoming trip to Pop ($49 a night!).
BTW--we probably won't see any 2009 bounceback offers until the fall. (just a guess).