persistent sessions - updating user data after 24 hours

[Aljosa Mohorovic]

1. fb user connects to my site/application and i can get user info,
like profile photo
2. user creates some content on my site
3. when user leaves (logout) i can't get his data anymore

how can i access user data (profile photo) after he leaves?
i have facebook api_key and secret_key from app but no idea how to get
data from users connected to app?
is there some way to get persistent session so that i can access
required data, profile photo in this case?

i often see facebook users profile photos on different site, mostly
comments. since data can be stored max 24 hours i guess there is some
way to get that info later?

Aljosa Mohorovic