I had a plan I was following, but got a shin injury about 5 weeks out from the marathon, and basically did no running from that point onwards.
I was certainly at the point where I thought I could run a marathon, and was throwing in a recovery week every 3 weeks, but I didn't do any strength and stretching of any note which probably played a big part in getting injured.
Like you say, I am very happy I got it done, but its pretty addictive running, and would very much like to have another crack at it in better condition!