Getting offline_access to work with Facebook

Question

I am using Facebooker with Rails to connect my application to Facebook. I can direct the user through the authorization process and through the process of granting offline access to my application.

How do I actually go about accessing the information offline? Is there a way to request a session_key that does not expire that I can use at a later point, so long as the user has not revoked the permissions for my application on Facebook?

Any help greatly appreciated. Advice need not be rails specific.