Not many hills here, but plenty of bridges and always the tmill for hills too. I like the direct challenge and focus hills bring to the training table.
The key isn't just lots of miles (though that helps) but lots of easy, *very relaxed* miles, which nurture and regenerate rather than degrade. Look at Ed in those videos of his jogging runs. He has incredible bounce for any runner, not to say one who has done the huge slow mileage he has. He has done a fantastic job in retaining his middle-distance form even when jogging. He looks like a miler doing a warmup jog, not a grinder shuffling to his next mileage goal.
I vary the terrain, and the distance constantly, though I am now far more consistent in my day-to-day mileage. I also do lots of pickups, plyos, stretching, weights, strides, short hills and a 10x100 on the track every 7-14 days. My legs are no longer "hammered flat", so I feel my stride has loosened and opened up up considerable in four months of this. The prospect of competing even at 400/800 next summer excites me now.
Sometimes I'll throw in a tempo mile at the end of a run. I haven't raced yet, just building a very large base. But have done a few track sessions that are extremely encouraging. Certainly for 10K-marathon this training I would think this can be done with little additional speed work, indefinitely. At least you'll beat the legions of old guys who are too beat-up to make the starting line.