Wondering what the various advantages/disadvantages of having a shorter Long Term Support (LTS) support period were over longer ones.
I notice Ubuntu provides 5 years of support, Red Hat Enterprise Linux (RHEL) has 7 years, and Novell has a 10 year support cycle.
Are these numbers essentially meaningless beyond 3-4 years (i.e., servers are replaced/upgraded by then)? Or is there a benefit to the different support durations?
This completely depends on the organization.
If you can get the devices to be upgraded on a 3-4 year cycle, then you don't need to worry about longer support; if your organization likes to avoid touching servers until they grind to an age-induced halt, longer support can be very handy.
I think you'll have to evaluate them based on your specific needs. Only you know the hardware replacement cycles your company has. In general for Desktops shorter is probably better. Servers benefit from the longer cycles, however my opinion is once a server lasts 10 years it becomes untouchable at an organization(in the bad way) like no one knows how to use it and is afraid to modify it. This can be the bad side of supporting something that old. Your going to be missing out on newer libraries, and the newer daemons(maybe that 10 year old bind doesn't support ipv6). Instead you should pick a release cycle you are happy with and plan your infrastructure around the fact youll have to upgrade the OS eventually.