freshman year, when everything and everyone i wanted was in a small area, i would just go and talk to people when i wanted to. no lag. later it became more of a stretch; if i wanted to go see my friends in the quad, it would take 15 minutes, which required planning so that i wouldn't get up there to find no one home. this is all obvious and i've discussed it before.
no, what i want to talk about is the other thing: because you have to plan in advance there's a good chance you will change your mind between the plan and the action, especially if you're as inconstant as i am. at four-thirty, i may feel like having dinner with someone at five, but at four forty-five i may have changed my mind. when i'm actually doing something i don't change my mind since all the stimuli dovetail, but the waiting period is totally different.
thus, it's easier to spend three hours doing something without changing my mind than it is to spend fifteen minutes waiting to do something without doing the same. because other things will be bombarding me; i don't have an isolation chamber to travel around in and prevent my mental state from changing too much.
now, it's even worse. some people, of course, are as close as they were in college, but others, like david alpert, are not. they're 45 minutes away, which, roughly speaking, means 75 minutes of planning, which means 75 minutes in which one can change one's mind via bombardment from other things. and of course for the people who live flying distance away, you have to plan things weeks or at least days in advance, which gives you even more time to change your mind.
this may be a major reason why people become less spontaneous as they age.