Marathon training and the long run????

Unless you are running 70+ miles per week, you won't be getting the long run in the 25-30% range.  Sure, maybe in the beginning but not when you start getting to the looong runs.  A 70 mile week would put a 25-30% long run at 17-21 miles. 

Pick one of the many popular ones out there (I have used Higdon's Intermediate plans 4x now) and trust the plan.  Someone like Higdon has had probably a million marathons run on his plans.  They are time tested solutions that work. 

IMHO - As a beginner, you are more likely to get either 1) burnt out or 2) injured if you try to do something like the Pfitzinger 18/70 plan (there is a reason it is called Advanced Marathoning) for your first marathon (those type of plans START at 53 miles per weak).

Good luck!

That sounds wrong, period. 26 miles is too far for a long run, especially on a beginner plan. It's a recipe for injury. Typically the longest run is 20 miles. I've never gone more that 22. OK, once, but we got lost.

Do NOT run more than about 20 to 22 miles for your Long Runs.  Much too risky, injury-wise when you get above that number.  I think of it as the "Injury-zone".  Not worth the risk.  You'll be fine on Race day if you finish a couple of 20s during training.

Bill

The 1/3 guideline is just that, of course. And I can't do much better than Scout's excellent answer. One can always diverge from guidelines ... it's just that the more you diverge, the greater are the risks involved. And the risks are probably greater the older and more fragile we become. In my 20s I was able to get away with a 'plan' that included a long run on the weekend and a limited amount of random stuff in the rest of the week, but there's no way I could get away with that in my mid-40s.

40 mpw with a 20 mile long run probably counts as pretty risky. This makes it almost inevitable that one run is far longer than the next longest run, meaning that it'll be very stressful on the body, and quite hard to recover from. One can do a marathon on that kind of regime, but it's not a good long term approach.

But even at 55 mpw, things can be a whole lot better. 55 mpw with a long run of 18 miles and a second run of 12-13 miles is consistent with the guidelines on not putting too much in the long run and not having the long run be too much longer than the next longest run. If you do a few weeks like this, and then throw in a run of 20-22 miles a couple of times, then that's a pretty minimal departure from the guidelines. 

QFT... After two marathons based on canned programs I am now seeing the value in consistently putting mileage month after month instead of just ramping up the 12 weeks before.

You also aren't balancing swimming and biking with your running, unless I'm mistaken.  While I know that most triathletes doing marathon training (including me) are generally back-burnering the swim and bike at least somewhat, many are still making time for at least maintenance workouts on both.  Speaking as someone in that category (and who has BQ'ed while still doing tri cross training), it's pretty tough to restrict your long run to 25-30% of weekly mileage, practically speaking...only so many hours in the week (and the swim/bike does count for something, aerobically speaking).

My peak week for my last three marathons ended up with the long run at about 40% (~20.5 out of 50+ miles)...for all my previous marathons, it was more like 50%.

Definitely rolling the dice on injury in that scenario, but definitely can be a practical necessity for a lot of triathletes looking to also do marathons.

Yes, it IS risking injury.

and unlike Scout, I think these plans result in more people getting injured, than actually making it to their target race unscathed.

I believe that a beginner marathon program represents the LEAST training a non-runner can hope to do and finish (within reason...we're all aware of untrained people that jump in last minute and walk to a 6+ hour finish)

To do a marathon successfully requires some long runs approaching 20 miles.  Without a certain amount of running behind you that is one heck of a shock to the legs.  So what do you do?  I suggest not following a beginner marathon plan. 

Instead, ask Scout to help you develop a plan and you will be light years ahead.

I don't have much to add. Go read Scout's response again.

I will suggest that my overall running fitness broke a plateau I had been at for some time when I began following Pfitzinger's programs and added a medium-long-run to my mid-week schedule. That'll get you a bit more volume and do wonders for your marathon training ... especially if you plan to race it rather than just finish it (not suggesting either approach is better). 

this.  Think of it a bit like this:  the long run is your support for the marathon.  the mileage during the week is your support for the long run.  without that base support during the week you are asking for all kinds of situations that may or may not include:  fatigue, injury, burn out, sense of failure....really, the list could go on and on and on......

   So what I seem to be hearing is that it is really best to work up to a weekly mileage that supports a few 18-20 mile runs, however if this isn't possible then breaking the rule for a few weeks/months may not be SO bad after all...hopefully. 

   I would love to put in longer weeks (ie. 50+ miles) but so far it seems as though I cannot get my body to run two days in a row.  I always seem to get some nagging pain when I run more than every other day.  This has been going on for probably a year and a half now.  This last fall I even stopped running for a month and then started a couch to 5K program and have been slowly building since then.  I recently went back to running every other day due to tightness in my Left knee that turned into pain.  Since I went to "every other day" the pain is going away. 

   I figure running every other day is an average of 3.5 days a week and even if I ran 10 miles every run, this would only be an average of 35 miles per week.  I hope I can eventually get to where I can run 5-7 times a week.