I was just having this conversation with my Mother in Law over the weekend. The entire family went to WDW for the Turn of the Century, we all bought "Lifetime" mugs at the All Star resort we stayed. MIL said she used her All-Star mug recently without an issue.
We took our All-Star mugs back in 2005 when we stayed at Music but have not been back to an All-Star since.
I know the mug debates get heated which IMO is just stupid but I did purchase a "lifetime" of refills - whether or not that was a reasonable expectation is not relevant. Disney sold me a "lifetime" as a marketing ploy and regardless of any new policy I personally feel that if I choose to schlepp my mugs back to the resort of purchase, Disney is obligated to honor the selling point which included lifetime refills.