Ditto what Darcy said about speed.

On weekdays I ride by time, cause I have to. Some days I get out of the office too late to ride at all. Saturdays, I am more likely to plan a route with specific mileage in mind.

However, I think you have to keep in mind what your goal is. Mine is to be able to ride where ever I want for what distance I want in a reasonable amount of time.