Last 7 weeks (specific incline's mimicing the course ascent- use of treadmil) and two week taper to keep your neuromuscular connection and tissues rested yet firing for race day! Show up to this plan after a 8-12 week base building training cycle. You should arrive at this plan with your "sweet spot" mileage you can sustain over the next 5 weeks to taper with your long run progressed to 14 miles.  Have fun- I got to the top of the mountain before all the other females by over 3 minutes and this is the plan I created and executed.