I suppose I have been programmed to believe that it takes 4 years to learn something: elementary, junior high, high school, college. It's a comfortable amount of time for a "stage." And it did cross my mind, when thinking about having a second child, that it'd be nice not to have both of them in college at the same time.
When I told my husband, he reflected and came to the conclusion that he prefers a 2 year pace. Do you have a pace? Or are we just weird?