Came upon this over on the wattage list. For me the only time I am "resting" or when my athletes "rest" is when they are tapering for a race. Aside from that... just keep on keepin' on.
"Recovery and adaptation happen all the time, i.e., there's no need to rest every X weeks for such responses to occur. Indeed, I am not aware of any data, or even a good theory, as to why this approach should be better than simply keeping one's "nose to the grindstone". There have been some studies of weightlifting claiming to show that a periodized approach is better (different type of periodization, though), but in fact they don't show what they claim to show."