I'm a 74-year old runner, and I've been running for over 37 years, including four marathons, and have had only one injury due to running. That injury happened in 2007 and was due to not giving my body enough rest. I had reduced my mileage while I was increasing my LSD pace. Then I started increasing my distance but made too big of weekly increments and was injured.
Because of my age, I have to progress at a slower rate, and I'm slowly getting back to the marathon distance. I've been running half marathons the past couple of years, and then because of my injury, I dropped my weekly distance down to 15 miles. Later, because of blood clots, I dropped my distance down to 0. Because of my age, I have to progress more slowly than you youngsters. I'm currently up to 10 miles per week. It will probably be around 2014 or 2015 when I run my next marathon.