I only run on days that end in a "y."

I am with you there. After last cycle, I've kinda concluded my body responds better to 70/week than the 80+. I just can't recover enough from the high mileage weeks to consistently succeed in workouts.

That 20 miler always seems to help boost the weekly miles. Have you ever tried to get your body used to doubles? I haven't yet, but it seems like a lot of people go that route to shoot their weekly mileage up. Not sure how my body would respond to it either.

SJ - I think my sweet spot is 65-70. With kids, a full time job that can get stressful, I just don't want to run any more that that.

Matt, yes, I have run doubles on easy days and hard days. During one training cycle I would do a hard 12-14 mile run that would include repeats or progressive miles, and then go out the same day and add 4-5 more to make a 16-18 mile day. My body held up but I can't say it translated in to a faster marathon. I am trying to train a bit smarter this time and see if that gives me more strength on race day. I am 46 after all. Maybe if I was 10 years younger...lol. But I think it can be a good way to break up easy days, too, so instead of having only time for a 7-8 mile run in the am run 6 early and 4 at lunch. Easy on the body but getting 2-3 miles more than normal. In the end I think it makes the most sense to make those hard workout days 10-14 miles by adding more miles before and after the hard part and going super-super easy on the recovery days. I think that gives one more benefit as it relates to a marathon then running 8-10 on a hard day and then 8 the next day. I would rather run 12-14 on the hard day and 5-6 on the recovery day. Just my two cents.

I don't look at 20 milers at padding mileage. I see doubles as padding mileage. I think there is a big difference in running, say, 14-16 and running 20+ in a single run, that I can't consider those freebie miles. Of course, I've never hit 70 mpw, like you guys, so take this for what it is worth.

I agree with both points of view. For me, there is nothing like 20+ miles, run frequently, to build endurance. On the other hand, I ran a double yesterday and plan to do it today. Early and late. My legs felt fine this morning, better than if I had run one long run yesterday instead of two short ones, but by the metrics I was obviously fatigued, I was much slower than normal at the same heart rate. So there is definitely a training effect going on.

Tom - I guess "padding" is not the correct word, it's just that when one puts in 20-24 milers the weekly mileage really goes up.

As for the benefits of running 20 miles, I guess that is an individual thing. I went back and reviewed my training leading up to my PR at CIM in December of 2011. It's hard to believe but through October and November I never ran 20 or longer (though I had 1 19 miler.) In fact, most runs were 16-17 miles. However, I ran some of those pretty fast, and on a couple of occasions ran as much as 13 miles at MGP or faster. Some of my weekly workouts were pretty intense, too. I think if one is putting in 3 runs a week of 12-17 miles then the need for those really long runs goes down. Many ways to train for a marathon but the mileage does need to be there in one form or another.

Agree on all counts. (2) 10 mile runs do not equal (1) 20 mile run. A hilly, MGP 16 mile run does not equal a flat, slow 20 mile run. I don't think I could perform well doing what you have outlined above. Even if it is only for the mental preparedness of the distance, I think need the 20+ milers, every now and again. In 3.5 years of running, I have only done 23 of them, and only one this year (I just checked). I worry that I will forget the distance / prep work involved, if I go without for a long time. I feel like I could do anything less than 10, with little or no planning @ rest, hydration, nutrition, recovery, etc. With 20, I might want to plan a little. just my 2 cents.

My strategy is to "forget" the distance, not to be reminded constantly of how far it really is. :-)