long lived user access token

JFBConnect automatically fetches a long-lived access token for the user, so that shouldn't be a problem.

The 2 or 3 days after login I need to send a message to facebook user timeline.

This is more complicated. While it's do-able, you need to make sure you follow Facebook's requirements. You can't post to their Timeline with a status update without their explicit permissions to make that post. You also shouldn't be making Open Graph Action posts if the user isn't actually on your site at the time performing that action.

We do have some code to make posts on user's behalf, but it's all intended for the user that's currently logged in. Can you let me know what you're trying to achieve (what type of post, user status update or open graph action) and what approval you're going through for the user, and we can gladly point you in the right direction for the code to use.

Thanks,
Alex