Quote Originally Posted by dominion View Post
I think if you're going for times rather than just getting round, you've got to do at least one - if not more long run over 20-22. At 18 miles, you've only covered 2/3rds race distance, and it's from that point where the wheels are going to fall off / hit the wall etc... I think it would be relatively easy to kid yourself that you're ready for a marathon on training runs up to 18 miles. 8 miles is long way when you're in unknown territory.
I would argue that you should even be doing a marathon in training. I remember seeing on Andi Jones's facebook that he did a 2:32 marathon in training six weeks before his back to back runs in London (2:18) and Manchester (2:26 in horrendous weather) back in 2012.

http://connect.garmin.com/activity/152673384

http://connect.garmin.com/activity/154949662

Pretty impressive stuff!