WHEN RUSSIAN RIVER released Pliny the Younger in February, 300 thirsty fans lined up outside the tiny Santa Rosa, Calif., brewpub for the first sip of this super-hoppy beer. Hop flavors fade fast, and for IPAs and even stronger Imperial IPAs like Pliny, fresh is best: It's on tap once a year and runs dry in days. But as the screechingly hop-forward brews of the craft-beer movement's first wave give way to deeper, more complex flavors, the revolution is moving down to the cellar. For some beer lovers, the best bottles aren't the freshest, they're the dustiest.

As...