The "base miles" people are talking about is critical. To put a finer point on my previous post- racing and recreational riding is great but week after week, month after month, year after year, it's hard to keep it going on with a consistency. Commuting on a regular basis is an excellent discipline and one that for many of us is easier to maintain.

When I fall off my road riding schedule I comfort myself with the fact that "at least I'm getting in 100 miles a week riding to work." it sure beats the yo-yo of getting really fit and fast for a few months then going sluggish for a few months then back to riding that many people do. I can't imagine a lifetime of the yo-yoing is as good for the body as having that nice base working for you.