To change the default session timeout (which is 5 hours (or 300 minutes)) you must edit the file web.xml. This file can be found in <YOUR DEPLOYMENT>/WEB-INF/web.xml.

(tick) If you are deploying JIRA as a closed .war file you will need to unzip the .war, edit the file, and re-create the .war with exactly the same structure as it originally had.

The element you want to edit in the web.xml file is:

<web-app ...>
...
    <session-config>
        <session-timeout>30</session-timeout>
    </session-config>
...
</web-app>

The value within the session-timeout tag defines the amount of time the session will exist, in minutes.

Note that after editing the web.xml file you will need to restart JIRA for your change to take effect.