I'm happy around 150-250 miles a week during the warmer months (includes commuting and cruising around town as well as road cycling). More than that and it's time to pay more attention to nutrition, hydration, etc. than I really feel like doing. To keep from getting bored, I like to mix in a few short/fast rides with longer (75+ mile) rides, and ride both solo and with groups/partners. In the winter, mileage and time go way down, though I'll still do a few weekly rides of over an hour outdoors in the cold and snow and continue to commute.

I'm also not a racer, nor do I aspire to become a road racer. Cycling is my main hobby and exercise - I always get hurt running, don't care for gyms, and dislike water (because I'm a cat, remember.)