Looking at the logic, whether or not the color changes. Filters are a very soft plastic that pick up dust and scratches over time even when stored and used carefully. We will demand that a lens be perfect without cleaning mark, fungus or dust. Perhaps not too far a stretch, the windshield on your car does not transmit the same quality image after 100,000 miles or so. Mine is covered with stone chips and crazing. Little scratches and dirt accumulate and will degrade your image. Relative to the cost of all the other photographic pieces we have, a new set of filters every so often may be a good cost effective investment.
John Powers