About three months ago, my 5.1.2 server here was somewhere around 300 days, and the only reason for a reboot was to convince a user that a problem they had wasn't with the server

I was gutted to have to reboot it.
I have a 5.6 one for a client which has only gone down for power or hardware problems - it's in a pretty foul environment. But it consistently runs for months at a time.
I have a 6.0b3 at home and it has only gone down for power, or when someone comes too stay - it's in a spare bedroom. I have too turn it off for visitors so they don't get disturbed by the noise. Must get it down to the garage......
Usually the only thing that takes them down is power, knackered fans making too much noise needing replacement, or swapping out dodgy drives from the raid. Perhaps I should invest in some pukka server hardware rather than cheap hacked PC based boxes.............
In my book that all that reads as Reliable software. Well done Mitel.
John