How much training is really necessary?

I was having a short chat on tonight's club run that got me thinking - how much training is really necessary to enjoy running a marathon?  From the short review of those around, it's not that much at all.

For my first marathon, I had a pretty solid training schedule for the first few months.  I don't have a log of it, but I'm pretty sure I was out 4-5 days per week, with long runs into the high teens.  Then I pulled a muscle walking into town and was out for a few months, strapped up my leg, and ran it anyway.  More than just a little stupid, but before the injury I figure I was clocking 30-40 miles per week.  (The scar tissue is still a bit of a problem now, due to the moronic need to complete the race)

The second time around, I was very conscious of the pain of the first time.  So, I picked up a Runner's World plan and was up to 40-50 miles per week, enjoyed the race (still the only marathon I've ever run all the way), and was forced to promise never to run another marathon again because I was spending so much time and energy in training.

In the past 12 months, I've run 9 marathons - 1 road and 8 trail, with less training than I ever thought possible.  Most of the success is down to reading that 1) 3 days per week is enough if you plan well; 2) making good use of recovery aids like massage, targeted nutrition, and compression; and 3) plenty of good luck. 

I remember a teacher from High School constantly pushed us to "work smarter, not harder", and have taken that concept on board in the past two years. Primarily, I've done this because I only get away with all of my running fun because I allow social activities and family time to interact with my training schedule.  The early forays into marathon training were more about running and sleeping than about fitting running into my life.  But, a secondary reason to spend less time on the run is that I just kept injuring myself.  The more time I spent running, the more frequently I seemed to need to spend waiting for something to heal.

So, what's my weekly schedule like?  1 long run, 1 medium run, 1 short run.  If I'm not preparing for a road marathon, then all of the long runs are on the trails.  If I've got a fast time in my sights, then half of them are on the road.  The other two are either tempo or the occasional long reps (away from races), social (most Monday nights), or  psychological refreshment (run whatever pace, anywhere, but just get out).  Most weekdays, I spend 15-20 minutes doing some core work and general body-weight strengthening.  That's it.  I like to think that the other 4 days are scheduled as "recovery".

Stats-wise, that equates to an average weekly mileage of fewer than 25 since January 2010. Over that time, only 1 in 4 weeks has been 30+ miles, and only 1 week over 40.  I regularly preach that recovery is a key part of training, but hadn't quite realized how much I had taken it to heart.  It will be interesting to see what I can do to squeeze in some extra miles once I've finished the constant cycle of marathon, recover, rebuild.