session expiration/notification

[Jim Newsham]

I'm using shiro on the server side of a client/server app.  The sessions 
on the server side are managed by shiro.  I have some resources which 
live outside of the session object, which I'd like to clean up when the 
client is gone.  I was hoping to add a SessionListener to shiro, so that 
I could rely on shiro to tell me when the session is expired.  However, 
I see that shiro expires the session lazily -- if I'm not accessing the 
session, I don't get an expiration event.

- Does shiro *ever* actively check for session expiration, and if so, 
how can I configure the interval?
- Or is that something I would have to do?  If so, how?  Where is the 
SessionManager.expireSessions() method? :)

Thanks,
Jim