STEPHEN STILLS His career at 60 years and counting, an icon looks back—and forward By Jeff Tamarkin Even at 82 tracks packed onto four CDs, Carry On, the new Stephen Stills retrospective boxed set, barely scratches the surface of one of rock’s most iconic careers. After all, how can one afternoon’s listening encapsulate a half-century of creativity? We first heard Stills in 1966 with Buffalo Springfield (“For What It’s Worth” remains...