I know it's annoying when you are logged out of your own local system withing a short period of time, right? You can set a custom Session Timeout value for Jenkins so you will not be kicked out of your system frequently. Simple open the following file in editor.
Then do add
JENKINS_ARGS. So the line will look like the following.
JENKINS_ARGS="--webroot=/var/cache/$NAME/war --httpPort=$HTTP_PORT --sessionTimeout=480"
Now what? Restart Jenkins service and you are done. :)