The DD39 GMC 'Jimmy' truck is still around. I'd imagine that the sets of more recent years, AK20 for example, because of their larger production runs, should remain affordable for longer. But you never know. (I might pick up another one for swaps, just in case. That could make it a self-fulfilling prophecy insofar as the announcement of immanent retirement actually boosts sales and hastens the end of liquidity in the market).