I have a new cabin with knotty pine interior paneling coated with water based polyurethane. At the start of the summer we hung several pictures. When we closed up the place in the fall we removed the pictures to lessen the chance there would be 'shadows' left where the pictures had shielded the pine from the natural darkening effects of the sunlight.
When we took the pictures down after 4 months I was surprised to see that there were already noticeable "shadows" where the area under the picture was lighter then the surrounding wall.
The question is whether even if we don't put the pictures up next summer will these lighter areas ever 'catch up' to their surroundings in terms of darkening? Also since we would like to have pictures would it be better to move them from place to place every year or is there any other way of dealing with it?