Thanks for the insight.

Acid-free paper sounds like the way to go. Do you have experience with this? Or is it common knowledge? Just curious!

I also read letters from my grandparents, stored by my parents in a simple shoe box. No special conditions, just light-free and inside the home for decades. They were still very much readable. I did not pay enough attention, but I guess it was blue ink from back in the day that they used.