Long exposures can give some very interesting results, but until you've done a few they surprise you. Or at least they surprised me.
Somewhere in my junk I've got a picture of a firetruck that's leaving after duty for a fireworks show. (No fires that night! Just standing by.) The exposure is about 40 seconds as I recall, and the people standing still on the sides are properly exposed. There is no recognizable fire truck in the image - only blurred lights, and even though I took the picture it still took me a minute to figure out what it was when I first saw the image days later. Had it been months later, and I had forgotten the "last frame" on the fireworks roll I doubt I would have ever been able to figure out what that blur was.
I do encourage you to do the experiment, but I expect you'll need to refine the technique to get the image you've envisioned.
From an artistic perspective, the photographer's job is to capture the preconceived mental image. (A. Adam's gospel there; you can disagree if you like.) So try a few experiments before you set up the 4 hour exposure. That way you can get some faster feedback on your technique before you set up the long exposure.
I suspect you're after trails following a figure. (Just a guess, so don't beat me if I'm wrong.) If so then take a look at the difference between the images here. http://www.shortcourses.com/use/using6-2.html
I know that may not be what you asked, but it might be what you're looking for. And if not then just ignore it.