I have all of the proof sets from 1955-2023. Not a single set is toned, discolored, or fogged. I chose reasonably pricy Intercept shield boxes. Which are supposed to help prevent such discoloration, fogging etc. the boxes close tightly and pretty much eliminate air infiltration plus all sets are in their OGP. Time will tell, I guess. Like you, Rob, I love proof sets! I don’t plan on breaking them up, submitting them for grading or anything other than saving them for my grandchildren. I bought six boxes and about $17 each for the sets.