Marathons is a subtopic of Running. See Running's other subtopics and posts.
Marathons are hard. I have run a several dozen of them and I still find myself involuntarily slowing with a few miles to go. It took many years before I got to the point where I could qualify for and run in the Boston Marathon at age 32, and winning the 2010 Davy Crockett Bear Chase Marathon in Texas.
Now my primary marathon goal is to run one in every U.S. state. Doing so by age 50 seems attainable.