I'm getting an offline access token like this:

https://graph.facebook.com/oauth/access_token?scope=offline_access&client_id=MYCLIENTID&redirect_uri=MYREDIRECTURI&client_secret=MYSECRET&code=MYCODE

obviously the MYCLIENTID and stuff have been changed for the sake of this post. Anyway, as soon as the user logs out of facebook, the key seems to no longer be valid. Am I not requesting offline_access properly (there's still an "expires" value on it, should there be if it is actually getting offline access), or is that just how it works?

If it's the latter, how can I get a key that will persist, regardless of if the user logs out of facebook? I'm sure this is possible, because Tweetdeck can still write to Facebook, even though I'm currently logged out.