At age 32, and being 10 lbs overweight, having never run long distances before,
I was able to get it from roughly 26 minutes starting out to a PR of 19:42. I ate right, dropped the 10 lbs, ran with guys who knew what they were doing (I had no idea what I was doing), and asked for eating and running tips from them.
It took roughly 6 months from April to early October and I was running most every day (usually 6 days a week).