NAPA VALLEY CABERNET doesn’t improve with age; it only gets older, a friend of mine contends. In fact, he added, the wines are just as good or perhaps even better in their youth. By way of example, he shared a bottle of 1999 Beringer Private Reserve Cabernet Sauvignon that he’d had in his cellar since it debuted. The wine was hollow, the fruit dried out. Had it aged badly, or was it having a bad night? Even after a recent trip to Napa, I’m not quite sure.

I’d traveled to the area to talk with producers famous for making age-worthy...