LOS ANGELES — Hugh Hefner leaned back on a red loveseat, the saggy one in the study of his infamous mansion here, and interlocked his fingers behind his head. A visitor had asked — more like shouted, since he has trouble hearing — a question about mortality. At 83, does he think about it? In a word, no. Mr. Hefner, the legendarily libidinous founder of Playboy, the prophet of hedonism, does not believe that his denouement is at hand. He doesn’t act like it, either. He still works full days on his magazine, flies to Europe and Las Vegas, pops...