Add this to the web.xml:
where xxx is a value in minutes (I looked in several places and didn't see any that said that '0' means indefinite). This applies to all sessions. As far as I know there is no way to configure sessions from a certain IP addresses.
OK in which folder under server/default/deploy do I find the admin console? ROOT.war?
Have you looked in server/default/deploy? I wonder what the admin-console.war directory is for?!?! By the way, you NEVER said which version of JBoss AS, so I assumed 5.1.0.GA. If you are using 6.0.0.FINAL, it is hidden elsewhere, so I'll leave it up to you to locate. ;-) If you truly cannot find it, and would care to divulge which version of JBoss AS, I'd be glad to help! (Yes, I am feeling somewhat snarky, especially when grepping for "admin-console" would easily solve this conundrum!)
I'm using JBoss AS 6.0.0 Final indeed. And... well I didn't notice the admin console being in the folder /common/deploy. Yeah grep really helped. Massively. :-)
BTW a session timeout of -1 seems to do the "never time out" trick: http://www.coderanch.com/t/174085/java-Web-Component-SCWCD/certification/session-never-dies