Well, at night it will make a difference!
My truck lights come on automatically, so I never worry about it. But during daytime, I think the only rule that should apply is, ... if the windshield wipers are "on", then headlights need to be "on" also.
Follow the rules of your state ... 30 minutes before or after sunset (which ever, I can never remember). Rest of the time ... I don't think it matters. An RV is not like a motorcycle. They are pretty big! You can see them coming down the road a pretty good distance away even without lights!
