In the mid-2000s I ran a. Fleet of RedHat servers that hosted millions of domains. I had boxes in that fleet that were up for over a year. Netcraft confirmed it!

Microsoft literally bought these 6 or 7 servers to migrate to IIS so they could “beat” Apache. It took more than double the servers, but after I did the initial work it was moved to a different team and I don’t know how the uptime compared.