Do you have appropriate storage space -- cool, dark, etc? If not, you either need to get a good place to store your investment, or forget about keeping it for 21 years. Too often one sees a cheap wine pulled from a cabinet over the refrigerator, or next to the furnace ( ! ), and people wonder why the wine didn't age well.
I'm hearing pretty good news regarding the 2007 vintage, but you'll have to hang tight ... the 2005's are just now being released. If recent history has any bearing, though, you might want to consider Washington State. Quilceda Creek has earned scores of 98, 100, 100, and 99 since 2001. The 2005 just went on sale today (and disappeared almost as quickly, though it will be available on some auction sites at marked-up prices). This winery is famous for making wines that seem to start to hit their peak after a decade and tend to want to last almost forever.
So, you want age-ability? Try a magnum (1.5liter) of Quilceda Creek, or perhaps magnums of Chateau Montelena, Dunn, Ridge Montebello, etc. from California ... when you take a premium, built-for-age wine and put it in a larger bottle format, you tend to wind up with something that can go the distance!