That's helpful. So if I follow correctly to get the page to function like he wants, he could add an a4j:poll to the page, having it poll some random data and, on expiration of the session, it would conduct the proper action.
if you post a poll to the server just 10 sec. before the expiration, the session timeout will start over. If the request misses the session timeout, onExpired will be invoked where the redirection to the '/login.jsf" happens.
However, I do not see why it is better than <meta http-equiv> mentioned above. If we need to keep the session alive while user does nothing but browser is open, the a4j:poll is helpful
And your poll will successfully prevent your session from expiration :-)
So, to be able to "verify" if session still valid on server from browser is not actually a simple task. The trick is to be able to make server call without associating current session with it. and be able to verify "validity" of that session.