I get the feeling it lost nothing over time, no increased fog, no larger grain (at least in 35mm). I compared a vintage print from a negative shot and developed when Panatomic-X was fresh... to a current print on freshly shot and developed but expired Panatomic-X. In terms of graininess, I can't tell the vintages apart.
Originally Posted by braxus
I believe our collective memory of its fine grain, is a glowing reputation earned through the passage of time.
It was a bit grainy and still is.
This is my own opinion formed on the basis of a limited test. This may not agree with your findings (you might still be right) or those of my employer, EKC.