He will go to the end of his physiology to find who he is and what he can do. Put himself deeper and deeper into a cauldron of pain. What is necessary becomes possible, however absurd the effort may be. But such interrogations, if they are to mean anything, should be infrequent. If the marathon is to measure a man, it should synchronize with the cycles of his growth.
Maturity is an uneven, discouraging process.
Becoming who you are is not done on schedule. There are years when nothing seems to happen. But one must still say that marathons can make memories like no other event in your life. And that could be an argument for running one every month. When the rocking-chair time comes, you'll be all set.