One of the wine world's great secrets is the aging potential of Australian wines. Australians know about it, of course. After all, they have been making wine for as long as Californians have, and there was no Prohibition to interrupt the Aussies' winemaking history. The idea just hasn't taken hold overseas, except among a few knowledgeable collectors. Americans accustomed to drinking Australian wines in the bloom of the wines' fresh youth may find this aging potential surprising. Only a small percentage of the world's wines survive over many years of aging and develop the kind of complexity that collectors treasure. Big, rich and barrel-fermented, or steely, crisp and delicate, the best Australian wines can emerge from a cold cellar and deliver the goods with the best of them.