Facebooker talk - Jul 2008 - how do I use the new infinite sessions?

I''ve got an existing webapp that I''m integrating w/ Facebook. 
I''m trying to wrap my head around a few things and I''d
appreciate some pointers.

It sounds like I would need an infinite session if I want to post a newsfeed
item to facebook when I don''t have a "recent" session.  Have
I got that right?

This post (http://developers.facebook.com/news.php?blog=1&story=116) led me
to believe that in the "new" version of facebook the only way to get
an infinite session would be for someone to check the "Keep me logged into
<app name>" checkbox at "Log in to the <app name>
application?" dialog.  Have I got that right?

If the above is true and someone did check that box at login, how would I know
that they did and how do I grab that infinite session key?

Let''s say someone logged in to my application via FB but
didn''t check the "Keep me logged into <app name>"
checkbox.  Is there a way recognize this state to drive them back to that login
page later?

TIA for the help.

----
We must be careful about what we pretend to be. - Kurt Vonnegut