Ultimate Facebook: How Long Should it Take for Automatic Retrieval of Facebook Comments ?

Hi

I have configured the Ultimate Facebook plugin and it's sending posts to my FB account when I want it to (via the Facebook Publishing section when I create a new post) so that's all good. I've configured the Facebook Comments section within the plugin the way I think I need to in order to have the plugin download comments from Facebook periodically (see attached screenshot "FB-Comments-Config.png" where it shows that I've selected the "Import Facebook Comments" option. On my site I'm only using the native WP comments and I think that's how I've configured the plugin.

I made a test post on my site "test post blog - FB", added a few comments on FB and imported them using the "import comments now (this can take a while)" link in the plugin settings panel. All worked well. I then added a comment on FB and left it for the plugin to import that single comment automatically, expecting it to be added to the post on my WP site like the others that were manually imported via the link. After 2 hours the comment had not been imported.

How long is the polling period for the automatic import with the plugin i.e. how long should it take? If I use the link in the settings page the comment is imported from FB immediately and added to the WP post on my site.

I have also attached a screenshot showing the FB app configuration in case that is useful.

Thanks for any help