We had 11 years of uptime on a VAX cluster at a company I worked for in the late 1990s.

They took it down in 2001 to replace it with something that took up 2U of rack space, about 2kw less power and ran windows 2000.

I turned up in 2012 to replace it again with something cloudy and it had 11 years of uptime (well done NT!) again[1] so YMMV.

The cloud based version has gone down about 10 times (thanks Azure!).

[1] not a great position but this was on an isolated network with locked down everything so less of a problem than a normally networked system.