According to a risk assessment conducted by the government of Australia — Food Standards Australia New Zealand (FSANZ) — advises that the shelf life of pidan (under the modernized processing methodologies for shelf stable production at ambient temperatures) should be about one year from production date stored at ambient conditions per labeling instructions and intact (they cite "USDA, 2006" as their reference).
In an informal context, I have personally been told by relatives (I am an ABC, of Taiwanese descent) that the shelf life is roughly as reported when stored in dry, ambient conditions, and that it can be extended "indefinitely" when refrigerated (with packaging intact).
Additional Reading
Effect of different alkali treatments
on the chemical composition, physical properties,
and microstructure of pidan white (backup)