silicon only degrades because of the prolonged exposure to moisture, im not a chemist so i dont know the process, but i do know that it happens.

this is why when electronics are stored away for a long time, such as HDDs, or IC chips, they are stored vacuum sealed with silica gel to pull out the moisture and keep it out.

Eventually every IC will fail on every logic board known in existence. it just depends on how well the chip is sealed away from the moisture. any porous chips will degrade faster than others. Is epoxy porous and will it absorb moisture and eventually get to the silicon die? I dunno but apparently so or they wouldnt ship certain ICs with silica gel.