here is a link to what the folks putting on Expedition Idaho are recommending for training. I particularly like the following excerpts:
In general… you need to do a few 24 – 36 hour trainings with no sleep, as well as with the same sleep strategies and systems you want to use in the race, including stowing them, carrying them, etc.
There is a for sure chance that at least some of you will be on the water at night. And it’s a big chunk of water. Really big...... [you'll need] kayak/canow skills and safety (like how to flip over and get back in – at night – in the rain) etc.
One of the biggest challenges at ExpId will occur in the trekking segments, and will require you to progress “on a bearing” through some very…um…challenging terrain…for a fair distance. There’s a better-than-odds-on chance of getting “off grid,” as they say, and ending up on top of the wrong mountain…which would REALLY suck.