incrediBILL - 7:07 am on Aug 24, 2011 (gmt 0)
I have a couple of dedicated servers that currently have 498 and 671 days of non-stop uptime at Server Beach and one of the old servers I shut down a while back had been up 3+ years.
As a matter of fact, my alarm monitoring service on a 5 minute test interval hasn't reported anything in over 2 years now.
The secrets are simple, solid hosting with top notch hardware, RHE OS, constant software updates to avoid getting hacked and plenty of server side software to stop outside abuse from overloading server resources
Going with low power cheapo servers or shared hosting is the easiest way to invite downtime IMO, a quad-core minimum, dual-quad preferred and enough RAM to handle burst traffic