That is, however, exactly what Clint Eastwood has done with "Flags of Our Fathers" and "Letters From Iwo Jima". Other directors have produced fine work at an advanced age. Certainly, Robert Altman was sharp even through the production of "A Prairie Home Companion", and he was at the top of his form when he made "The Player" and "Short Cuts" at an age when most people have long since retired. Hitchcock was 73 when he made what is my favorite of his films, "Frenzy".
I can't help but admire these guys and hope I'm lucky enough to be productive that late in life. David Thomson takes a look the movies made by directors after age 70, including Renoir, Zinnemann, Kurosawa, and Bresson.