Jon Gould is a nationally-ranked endurance mountain biker and was part of the second place team at this year's Trans Rockies Challenge (after 7 days of racing he lost by less than 2:00). There is an interview with him at EndurancePlanet.com which not only talks a bit about the race and his experience, but also his preparation and nutrition for the event. EndurancePlanet.com hosts weekly podcasts with interviews from a multitude of endurance athletes from triathlon, cycling, mountaineering, etc., etc.
You can download the mp3 via this link.
*Note that when he says each stage lasts 4-6 hours, he's referring to himself and the other pro riders. Amateur riders typically take between 6 and 10 hours per stage.