Before we delve into the topic of server upgrades, it is important to define the terminology. With a Linux-based operating system, an “upgrade” refers to the latest snapshot packaged by the distribution’s developers. That usually includes a newer kernel version, newer libraries, and more recent software packages.
In addition to these upgrade snapshots, most Linux distributions will provide periodic updates over the life of a particular version. For some desktop distributions like Ubuntu, the version life is very short, except for long-term releases, and the distribution is upgraded twice a year. After a new version is released, a distribution may keep offering security updates for a year or even longer. Red Hat, for example, will support releases of their operating system, Red Hat Enterprise Linux, for up to 10 years, with their Extended Lifecycle Support (ELS).
With that in mind, it is generally not necessary to perform an in-box upgrade to a production server, and the risks may be too great to warrant even trying an upgrade. As long as your operating system still receives the latest security updates, there is probably no good reason to upgrade.
The one exception, when upgrading may be useful, is when there is some significant improvement that only an upgrade would give you, but this is a rare occurrence. In most cases, you can install newer versions of software without having to perform a complete upgrade. That only leaves the kernel, and with dedicated servers, new kernels do not usually offer dramatic improvements.
For remote server hosting, like that offered by 34SP.com, it is usually a better idea to upgrade hardware at the same time you plan to move to a newer version of your OS. In such a situation, you can migrate your data and websites rather than performing an in-box upgrade.