A couple of years ago, the coach of an elite Cincinnati-area team told me that competitive runners continue to improve their race times for ten years after they first start racing, no matter what age they start.
This was heartening. Discussions with certain non-runners involve smug warnings about the invisible injuries I'm causing myself at my advanced age, and dire predictions of the decrepitude and disappointment this will all end in, hopefully soon.
Two years ago, in May 2009, I started racing again at age 44. I'd raced one non-injured cross country season of high school; and three 5Ks the summer I was twenty-seven and getting over this guy Mark. According to my calculations, that gives me at least nine good years from when I started again, or maybe even the full ten. Which takes me almost up until my entry into the 55-59 year old age group in 2020. My goal is to see how good of a runner I can get to be in the next decade.