6.5 mostly-flat miles was how I got started, too. I thought I'd do it a couple of times a week and build up to more days, but after the first day I thought it wasn't so bad, so I just kept doing it. On the first few Fridays I was a bit sore but not bad.

My wife and I moved last month so now I'm only 2 miles to work. I feel like a lazy slob.