I'd be inclined to agree about finding the product 20 years from now if not for the fact that it seems we are all bunkering anything we hear is on the way out. For instance, I have 14 bottles of OC 12. And I'm not the only one. I haven't seen any in Dallas in some time (except dusty Louisville bottles). I think the quick dissemination of information on any discontinued bottlings coupled with the increased popularity of bunkering on sites like these (not too many references to it in threads from 3-4 years ago) means the bourbons that vanish from the market vanish from the shelves. In traditional dusty haunts, many of the bourbons we're talking about going away now were never on the shelves to begin with.
At any rate, I won't bunker much Weller Centennial, if any, but Weller Antique...that's a horse of a different color.