For the 3-4 month period over the Summer when i did a majority of this training i was doing nothing strenuous at all for the remainder of the days. The rest of the day would usually consist of relaxation, eg reading, playing video games etc. The only other thing worth mentioning is that i worked 10 hours a week (2 x 5 hour shifts) stacking the dairy/freezer sections at a supermarket. I had very few stresses and my sleeping patterns were very regular (at least 8 hours every night).

RiphRaph, you seem to be implying that riding for only 10% of your day is insufficient to cause persistent fatigue. I disagree. 1.5 - 2 hours of high intensity mountain biking everyday (with no rest days) is still a very high exercise load.