Lines

Taking a break from work for a moment (yeah, I'm here on a Sunday...). Thought I'd talk about something that I think is interesting and I'm starting to notice:
For a long time I didn't have even a marginally decent grasp of line, but it is something that's finally starting to (sort of) make sense to me- that is, the mechanics of a line and how they work to carve out space and describe interrelations among forms that exist only in your mind. Now, my first point that I'm going to try and communicate with this is that a line cannot be judged solely on its angle, or thickness, or tangency, but in the manner with which these things change. When being viewed, a line is transformed into a temporal space, and becomes animated in its own right. Granted it is a still drawing, but it takes time for your eye to traverse the stroke, and it is over that time that there occurs a change of shape.
I've noticed this has been overlooked by many new students of animation and design... we're often told that our keys make or break a scene. Time spent getting those poses right is essential to communicating your idea. Yes, but. As many of you know its the manner in which you change those shapes IN A TEMPORAL CONTEXT that tells that idea in a nuanced/interesting/worthwhile/(believable?) manner. It isn't enough to have only the beginning and end of a line planned. WHEN does its angle/thickness/tangency change along your intended path? HOW LONG does that change take? Do all the elements change AT EQUAL RATES, or are you offsetting them? These are all things that are shared in both animation and design, and invariably give you a much much better chance of getting your drawings off the page. Thoughts?