+1
I was going to mention this as well. Throw in some road rides because even hard rides on the trail do not have the same benefits that a road ride has when it comes to improving your aerobic capacity. I can feel a difference with even one hard 50 or 60 mile road ride on the weekend. The other thing I recommend doing is doing some hill repeats on some of the climbs of the EB. You're going to be doing these hard hills after quite a few miles. Start by doing something like Yaupon or Coutyard 2-3x, take your time between them, play with your gears and/or pace. Even if you plan on walking these during the EB, they will improve your fitness and prepare you mentally as well. Ride them on your MTB so you know what to expect.