Thank you for all the great suggestions. Mauro: the DVDs are only one method of long-term storage we are using. They are, however, the most user-friendly for our researchers, so keeping them in good shape but still identifiable is critical for daily use. I am investigating purchasing gold-based DVDs for our archive copies, but keeping the regular DVDs for public use. The manufacturer of the gold-based DVDs contends that his product is good for 100 years. Guess he figures neither he or his clients will be around to face the inevitable lawsuits.