It's a matter of choice but tend to put ours on, we leave a small greenhouse fan heater on frost setting so makes warming the van cheaper ( don't lose so much heat via screen) keeps sun off upholstery. Screens get dirty but wash off, does not seem to affect their life as had last set 8 years and sold with van (model change) and have seen them still in use 2 years later, on a site.
Dave
