When sharing or viewing old photos I have never had any concern of the quality of the image, nor have I ever heard anyone else mention this either, unless it is "it's amazing how great these photos look for being over 100 years old." And I can't vouch for how long they will last. I only know I have prints that are at least 100 years old and have many on our home walls of my wife and I when we were babies, so at least 81 years old and nothing seems to be wrong with them and they have been exposed to light for the entire duration. The real keepers are kept in albums and in boxes so they are only experience exposure to light on short occasions.