Pre pre planning for an IM

I didn't do a stand alone before my first IM.

I did one full Mary about 4 months prior.

My first mary will be at the end of IMAZ this Nov.  And longest run to date will be 18 miles.

I haven't done an IM, so take it with a grain of salt, but I am a big believer that the most important part of the run is getting to the beginning of the run ready to run 26.2.  IOW, you can be a 3:30 marathoner but if you don't have the swim and bike fitness and you get to the run gassed, it doesn't matter. 

Yes, run training is obviously key, but from my understanding you don't train for an IM mary as you would a stand alone mary.

5 marthons before my first IM. 

The one experience and skill that I learned from preparing for a marathon was training consistancy.  A common denominator of a marathon and an IM is they both take serious, consistent training for a sigificant period of time.  That is not to say I trained hard for ALL my marathons but I trained hard for enough of them to learn the difference in how I felt when I trained right and when I didn't.

If you trained hard, consistently and for a long period of time for your marathon, I'd say the step up to an IM is not that big of a leap.  You already know what it means to get up early and go for a 3 hour run....all you need to go is get your mind around dong that the day after you spent 5 or 6 hrs on a bike.  :-)

~Mike