Cat - I live not too far from you in super-hilly land. I can't ride any more than 4 days a week, or else I'm just wiped, then get a cold. I don't know why, just the way my body is. I do weights and some yoga classes at the gym 2 days a week, then just walk on my "rest" day. Even during the winter, I can't do more than 4 hard work-outs a week without getting sick. My mind wants to do more, but my body just can't do it. And I'm in my late 30's, so I don't know how much age really has to do with it. Maybe it's more genetics?