How far to walk?

Howdy folks,
We're taking a break from our action\adventure to talk abotu something that most of us probably don't think about. As the title implies we're talking about characters walking while deliver dialog.

You'd probably wonder how that is important but if you think about it distance can make or break a scene. If your characters have two minutes of dialog but only walk for one minute the scene is long. If your characters have one minute of dialog but two minutes of walking it's now too short.

I just hit this exact problem with a script and found that clever editing and filming will allow five minutes of dialog to last for a cross-country trip. A good example is "Little Miss Sunshine" which had them going a long way but the movie was only 2 hours long including hotel stops and the like.

I've also come to the conclusion that green screen can be used for this kind of thing though it still requires the same editing to insert the background correctly.