To make it configurable on a user-by-user basis, the development effort would be enormous and would add a lot of unnecessary complexity for such a simple feature.
To configure it for the Camunda Webapp, go to $WILDFLY_HOME/standalone/deployments and insert the following snippet into the WEB-INF/web.xml of your camunda-webapp-ee-jboss-7.4.5-ee.war:
<session-config>
<session-timeout>30</session-timeout>
</session-config>
Or you could change the default session-timeout Wildfly sets, when a web application does not specify one.
This seems to be possible by modifying the undertow subsystem configuration, see this thread in the jboss developer forum.
Copied from the thread:
<subsystem xmlns="urn:jboss:domain:undertow:3.1">
<!-- ... -->
<servlet-container name="default" default-session-timeout="30">
<!-- ... -->
</servlet-container>
<!-- ... -->
</subsystem>
Cheers,
Christian