I'm nearing the end of the C25K and am considering where I want to take this new hobby. My dream is to be able to run marathons someday. Not to compete, just to complete. Does anybody know how long it would take to get into the kind of shape that can run 26 miles? I used to be able to walk that far but it has been a few years since I tried it. I have always had the problem of pushing myself too fast, causing injury. I really don't want to do that again, since this running has been good for me.
I would say to take a year and a half to two years. Build your base and do some shorter races along the way. Work your way up the ladder so your body has time to adapt. Once you get to the marathon point, your training plan will be 16 - 20 weeks anyway. You'll be a lot better off if you get there gradually.