What can I do to prevent sun-fading of my floors?

Discoloration of the finish (and in cases of intense, direct sunlight of the wood itself—certain species such as cherry are notorious for this) is normal and unavoidable. Oil base polyurethane finishes are most susceptible to this phenomenon, which is called photochemical-reactivity. While waterborne finishes are often advertised as non-fading, this is not true (although they discolor less than oil base finishes). Use of blinds or drapes to block direct sunlight will help, as will use of newer window products which reduce UV transmission. While most discoloration is caused by sunlight, finishes will also amber and discolor with age. Moving area rugs and furniture on a regular basis will help to minimize the stark contrast between areas with sunlight exposure and those areas which have been shielded from light.