Another duty of the system administrator is upgrading and installing new software.
The Linux community is very dynamic. New kernel releases come out every few weeks, and other software is updated almost as often. Because of this, new Linux users often feel the need to upgrade their systems constantly to keep up the the rapidly changing pace. Not only is this unnecessary, it's a waste of time: to keep up with all of the changes in the Linux world, you would be spending all of your time upgrading and none of your time using the system.
So, when should you upgrade? Some people feel that you should upgrade when a new distribution release is made---for example, when Slackware comes out with a new version. Many Linux users completely reinstall their system with the newest Slackware release every time. This, also, is a waste of time. In general, changes to Slackware releases are small. Downloading and reinstalling 30 disks when only 10% of the software has been actually modified is, of course, pointless.
The best way to upgrade your system is to do it by hand: only upgrade those software packages which you know that you should upgrade. This scares a lot of people: they want to know what to upgrade, and how, and what will break if they don't upgrade. In order to be successful with Linux, it's important to overcome your fears of ``doing it yourself''--- which is what Linux is all about. In fact, once you have your system working and all software correctly configured, reinstalling with the newest release will no doubt wipe all of your configuration and things will be broken again, just as they were when you first installed your system. Setting yourself back in this manner is unnecessary---all that is needed is some know-how about upgrading your system, and how to do it right.
You'll find that when you upgrade one component of your system, other things should not break. For example, most of the software on my system is left over from an ancient 0.96 MCC Interim installation. Yet, I run the newest version of the kernel and libraries with this software with no problem. For the most part, senselessly upgrading to ``keep up with the trend'' is not important at all. This isn't MS-DOS or Microsoft Windows. There is no important reason to run the newest version of all of the software. If you find that you would like or need features in a new version, then upgrade. If not, then don't. In other words, only upgrade what you have to, and when you have to. Don't just upgrade for the sake of upgrading. That will waste a lot of time and effort trying to keep up.
The most important software to upgrade on your system is the kernel, the libraries, and the gcc compiler. These are the three essential parts of your system, and in some cases they all depend on each other for everything to work successfully. Most of the other software on your system does not need to be upgraded periodically.