Haven't we basically already built them? They're just slow and not supported by software vendors so nobody wants to use them. Other than replacing capacitors and realtime clock batteries on every 20 years or so, dusting and replacing fans when bearings go bad (assuming it's not a passively-cooled design), most computers should basically last beyond a human lifetime (I've read that those less than ~20nm will go bad over time as traces lose atoms and eventually fail, but older processes should be fine).
However the older solders have a much higher percentage of lead in their composition which makes whiskering less likely. I have two Zenith Z-120s made in about 1980 and thus coming up on 50 years old which don’t have any issues.
I know of a running TRS80 and a BBC Model-B, but the retro-heads who
own them jst pwer them up now and then, not in constant use so as not
to heat-stress them. TBH they smell a bit. My theory is the
transformer windings are on the way out.
Yes, we have. I have a few computers that old or older, and they run just fine. Every so often a dried-up capacitor has to be replaced, but that's about it.
