In reply to JMGLondon:
> Managed to dip under 3 hours (just) on Sunday for the first time.
Congratulations, that's a big psychological milestone IMHO and a massive physical achievement.
When I was aiming for 3.15 in Paris and surprised myself with 3.07 on the back of little marathon-specific training (I'd been running trail races, a mix of 15-30k stuff every month and one or two ultras a year) I thought if I cut the mountains, trained scientifically on the road I could beat 3hrs.
I chose Amsterdam in the autumn (since in the Alps it's hard for me to train for the road over the winter), ignored all the beautiful trails and pounded intervals and SteadyState runs on the road. In the end I beat my PB by 1 minute at 3.06. That's a long-winded way of saying I think I'd discovered the law of diminishing returns the hard way.
After that I decided I'll stick to off-road stuff where you can't compare one race to another since there are so many variables and I wouldn't get stuck on set times/paces. And also the training is much more fun.
A friend of mine ran London on Sunday and was disappointed with 2.42 because he'd been chasing sub-2.40! Madness.
I'm sure I'll do another road marathon one day though just out of curiosity to see how much I'm slowing down with age.