I wonder how long original ULA's would stay in working order if just stored
under normal (+/- room temperature, not too dry or moist air, no direct sunlight etc). Let's say, starting with little used or N
tock parts. Maybe power up once or twice a year (under carefully controlled conditions) to check if still working.
Verdict on that is still out on that for IC's in general. IC's only exist since the late 50's, early 60's or so. And some of the very earliest IC's ever made are known to be still working fine (especially well-built IC's in ceramic packages etc). But Sinclair ULA's are not like military-spec, hermetically sealed ceramic package. And not full custom but gate array + customer defined interconnect layer. Similar but not the same as a mass-produced single purpose IC.
Sealing between external pins and internal silicon die, bond wires etc may not be 100%. Or plastic used may
allow gasses/pollutants from outside world to leak in. Veeeerrry little, veeeerrryy slow of course, but still some
, and leaked in molecules doing their destructive job. Not to mention high-energy cosmic radiation, or whatever else may attack / degrade the inside of IC's (let's assume ESD precautions are adequate).
40 years? 50 years? 60+? Will they die en masse after a certain age? Or will there be a very 'long tail' with some specimens surviving say, a century or more?