What's the 18 week program Matt?
It's from a book called 'Advanced Marathoning' by Pete Pfitzinger and Scott Douglas. A great read with marathon training plans ranging from 55 to 100+ miles per week. I'm doing the 18 week up to 55mpw plan
https://www.youtube.com/watch?v=_3tCVxm0sm4&spfreload=10 Check it out
I will give that a watch!