I just finished off my third bottle of the 25yo. And I probably will not see it again. I had bought one, as soon as it was empty, I had another one on hand. And then I bought the last one at the market, becuase I thought that it would be the last chance to get it. And so far it has been, and I miss it. I have been seeing the 21yo around, but at even a higher price point. So, I have not been tempted yet.
I remember there being a lot of variations as to what was in it, from very old Highland Parks, to various Speysides... I never got a definitive list of the mix.