A lot of Linux distro is into the change every 6 months cycle. While this can foster advancement, change is not always good. The hardware on the computer typically may not change. A new release may deprecate your hardware. This is more of a problem for older machine.

One thing not talked about is backport support. Even if your Linux distro doesn't change, you may want to upgrade to the next version of the application for security reasons (perhaps your version of the software has cease to release security patches, or is this generally handled by the distro as well?). This is in some ways where Windows seems to have an advantage. Right now, I haven't upgraded to Firefox 3 on my Linux box but have upgraded to it on my Windows box.

So which distro generally have good backport support?

Paul

RHEL (and CentOS since it is compiled from RHEL sources).

As an example: There was a major BIND exploit recently announce. RedHat backported the fix into the official release they use (9.3.4-P1 on RHEL5 for example) so that you didn't have to go roll your own and upgrade to 9.5x versions. The backport they did fixed the port randomization - I only had to yum update my BIND packages (and modify named.conf but that had nothing to do with them).

Of course the downside is it looks atypical to the folks that make BIND. If you tell them you're running 9.3.4-P1 they think you're using a vulnerable version.

RHEL supports releases on a longer basis because it is used in commercial environments where upgrading the OS every 6 months simply isn't an option.
Fedora on the other hand is bleeding edge so has a much more aggressive rollout schedule. It is used as beta-testing for what ends up in later RHEL releases.

I imagine for the same reasons that SLES is similar to RHEL rollouts but I don't work with the Suse stuff at all.

Debian has the probably the best backport support among all OSes.
Ubuntu has good support too.

Assuming you don't mind bugs that restrict random key generation for SSL/SSH.

Reine agrees!

If a paid version of a disto is based on an open one, that open one will probably be supported for as long as the paid version is supported.

For example, SLES 10 uses the same packages as openSUSE 10.1. You could stay with openSUSE 10.1 if you can stomach it's lousy updater. Getting rid of the mono based update system was the best thing that openSUSE did in 10.2 IMHO.

Linux Mint has a Mint tool that back ups the home folder