Irrepressible writer-comedian Carl Reiner, who shows no signs of slowing down at 94, monitors a few others over 100, and nonagenarians, to demonstrate how the twilight years can truly function as the happiest and most rewarding. One of people who share their own insights into what it takes to be productive and crucial in older age are Mel Brooks, Norman Lear, Kirk Douglas, Dick Van Dyke, Betty White and Tony Bennett.