In the 1980s AT&T was designing cabinet-sized minicomputers that would have less than 2 hours downtime in 40 years and went to great lengths to enable software update without reboot (functions accessed via transfer vectors) and ability to survive and continue running through earthquakes. These are still running I gather as part of various phone switching systems 4ESS, 5ESS although the hardware has been "reengineered." https://en.wikipedia.org/wiki/3B_series_computers .