I found myself using the same TeX distribution for years, without updating it. This is not a problem usually, unless you are asking someone else to look at a particular error or problem and that person is working with another version and therefore may not be able to reproduce your issue. The TeX Live distribution is evolving, i.e. packages are extended, replaced or added and therefore it is a good idea to update your distribution once in a while. TUG provides an updated image every 1-2 years.
Windows:
If you have MiKTeX installed (part of proTeXt), there is a program that you can run in: All Programs -> MiKTeX -> Maintainance -> Update. This will open a dialog that helps you update the distribution.
Mac OS X:
Under Mac OS X, the TeX Live distribution is called MacTeX. It contains a neat little graphical application that lets you update your distribution. The application is called “TeX Live Utility” and can be found in Applications -> TeX. It has a built-in update function to keep the application itself up-to-date.
If you prefer the terminal, try:
sudo tlmgr update --self sudo tlmgr update --all
Linux (Ubuntu):
It is a little tricky to update TeX Live under Linux and as usual depends on the distribution as well as your local settings. So below I describe the way I did it on my computer. It should at least give you an idea how to do it or what you may have missed in case you run into some problems. I am running Ubuntu.
I leave it to the reader to decide what he is more comfortable with, running commands with sudo or change the rights for the texlive directory you are updating. I will use the latter approach here. Set the username accordingly as well as the install directory if it differs.
sudo chown -hR your_user_name /usr/local/texlive/2010
If it has not been done before, add the install directory of the TeX Live distribution to the path. The tlmgr-command (texlive manager) is in that directory.
export PATH=$PATH:/usr/local/texlive/2010/bin/i386-linux/
Next you have to set the location where you want to update from. This has to be done only the first time you are updating. In addition, you may be asked to update “tlmgr” also in case there is a newer version.
tlmgr option location http://mirror.ctan.org/systems/texlive/tlnet
and
tlmgr update --self
Finally, you are ready to update the TeX Live distribution.
tlmgr update --all
This final step may take a moment, time for a coffee.