The black marker has stood up pretty well without fading or bleeding.
What happens with the actual paper? Does it degrade or thin? You see really old stuff it always seems delicate and brittle. Does paper have a "life expectancy" for lack of a better word?
Now this is a very good question - the kind I enjoy answering. Originally "paper" was made from linen fibers. Think "papyrus". Lasts a long time. Once paper was made from hemp - even stronger. Most great paintings are on hemp. Then, lets skip to the 1800's and the Industrial Revolution. Cheap wood pulp - hence the "penny dreadfuls" like "Varney the Vampire". Turns to dust in a few decades. Point is, the life expectancy will be contingent on the composition of the paper in question. A 1940's sulfur rich album page, like newsprint, will degrade, embrittle, yellow etc. A quality wedding invitation for Burton and Taylor might be of better stock and have a much longer life. Remember the ink has a part. Some iron based black inks wuill "burn" the paper as it oxidizes. It all depends on what you have.
I believe one should not pay full $ for a sig on a self destructive album page.
Thank you for asking such a relevant and important...perhaps overlooked question. I hope others will add to my attempt at an answer. The combined knowledge here is inestimable.
Something in the 45 pound, flyer stock variety. While not sealed it has been primary covered and away from open air and sunlight.
It's 32 years old next month.