When a Ubuntu release reaches "end of life" it receives no further maintenance updates, not even critical security upgrades. It is highly recommended that you upgrade to a recent version of Ubuntu at this point. Please check the download pages for more information.

Normal Ubuntu releases are supported for 18 months. Previous Ubuntu LTS (Long Term Support) releases were supported for 3 years on the desktop and 5 years on the server. However, starting with Ubuntu 12.04 LTS, LTS releases will be supported for 5 years on both the desktop and the server. During that time, there will be security fixes and other critical updates.

The ubuntu-support-status command will print the exact status of your system.

For more details of previoud and upcoming releases and please see the Ubuntu wiki.