Thanks for that nick, this thread is from this time last year as I was starting my marathon training, which went pretty well, all my runs over 2 hours were on an old dissused railway line on the way home from work, you could say my long runs were all mixed terrain, bits of everything, but not one of my long runs was solely on road. I know what you r saying about cadence and that, but I think you find it easy to keep good cadence if you are not struggling!!!! you cannot keep good cadence if your legs are whacked!!! Threshold training is good, I did most of that on the treadmill.....
I got 249 on a hot day last year, this year im running a lot better and am hoping to dip under 240 :-)