First time I tried Couch 25k about 18 months ago I got to week 7, with a bit of stopping and starting, in about 4 months. But life kept intervening, and I had to change my schedule, from running at the end of the day to running in the morning. Boy what a difference that made! Suddenly my muscles couldn't take it, for the very first time! My daughter basically explained if you run before eating you burn off glycogen and that's what causes muscle pain - good for losing weight but hard for stamina.
Second time I started I got to week 4 and then someone promised me a pair of Vibrams. (Jammy, I is.) So I thought I'd better start again with them, and with one thing and another, didn't get going till 2 weeks ago. Week 1 went swimmingly but by gum my pore old knees could hardly take me up the stairs for a whole week after. So I gave them a rest and I'm repeating week 1 this week. So far so good, it is a different way of running and I'm hoping it's going to be lighter on the joints. In the end. Fingers crossed!