If it helps this is what they have printed on Allearsnet.com about the mugs:
Most of the WDW Resorts have a "Refillable Mug" program in their food court area (aka Fast Food-Counter Service). You purchase a mug for around $11.99 and are entitled to "free" or less expensive refills for the duration of your stay. The refills are available from the beverage dispensers and usually include: coffee, sodas, ice tea, and hot chocolate. No other purchase is required to get your mug or your refills.
The mugs have the hotel logo on them and signs state that they are for use at that hotel for the duration of your visit.
For an avid coffee or soda drinker, especially with the 'free' refills,
you can't beat it.
The table below outlines the refillable mugs available at the resorts and the purchase as well as refill price. Be sure to add 6% tax to the purchase price.
In that explination where does it say that those mugs are no longer good once your vacation ends. Also it does not make reference that the old mugs with no explination on them, which people think should not be used. So there is nothing there to proof that the mugs my family & I purchased at the Contemporary in January 2000 are no longer good.