run forest, run...
...You really do want to get a solid, adequate training schedule in though. The difference between being in good shape and being ready to run a marathon is hard to overstate.
fully agree with this statement. running for fitness and training up for a full are way different. general rule of thumb would be to be running more than 35 miles per week for several months as a base PRIOR to starting to ramp up for a full.
...Second being that marathons are not good for you. They are a mental challenge, but they are not good for you physically.
don't agree with this one. if you have done a good job training for it and getting ready, it's just another race. if you run the full without the proper training, then yeah, you might do yourself some damage.
...It's cool to run a full marathon once or twice in a lifetime and it's cool to be able to go through "the wall", but running a marathon is a major stress on your body, so you should not do it too often. From what I've read, running for 2-2.5 hours is the most one should do, after that it does more harm than good.
as above, it's all about the training and prep work. it is a major stress, and most pro/coaches would limit the number of fulls you run in a calendar year, but that's to achieve full recovery before training up for the next. don't run/train in a weakened condition as it were.
i ran 3 fulls with several months between in '95, and then ran a full and an ultra (50 miles out to the turn around point, then back) in '96 with no problems. i think it comes down to body type and interest. i can't bench more than about 200lbs, but i can run forever. just my 2 cents.
a quick bit on training, it's more than just putting in miles. that's important, but so is the stretching, and just as important is the strength training. running by itself tends to develop specific groups of muscles in the legs, and strength training to counter balance that is really important. running intervals, running hills/steps, doing tempo work, and working on proper form are all equally important. to do it right and be ready to go takes a bunch of work, but i say worth it in the end.
last, get fitted by an expert that can recommend the correct shoe for your foot. the teenager working at foot locker in the mall is not the correct answer. they should be able to help you pick the correct 'last', evaluate your stride/strike, and pick a shoe that matches your (under/neutral/over) pronation. anything else, you're just asking for pain/injury. there is no 'best' shoe, only 'best shoe for you' and anyone who says different is working on commission...
i'm getting ready to run a full this fall, and can't wait. nothing like race day and a free shirt at the finish line!
best of luck.