Hillary Trail 71Km run

So I'm running the 71Km Hillary trail. I've got 8 weeks to get myself in order for this. I'm upping my long runs from 2.5 hrs to 4hrs and plan an 8hr day out running and walking. I'm going to stick to my usual running pattern through the week as it's a great lactic threshold and VO2 max stress routine. I'm going to have to get used to eating on my long runs and will have to carry a heavier pack than usual. I think the run will take between 12-14 hrs. It starts at midnight so will have to start training in the dark. It's an extreme off road/mountain trail through bush, rainforest and rugged coastline. What on earth am I doing?