XF 1.5 Post refresh times

On posting up new posts, it seems to take ages before the new post displays the actual change and author. It also takes a while to come through onto the " recent threads " area.

any way the refresh can be opimised and if so ..... where / how can I do it.

many thanks for any input. Much appreciated.

So far in order to force the refresh, I have to go outwith forums, say to the media gallery, come back into the forum and the change seems to happen. Puzzled. What or where is the refresh page / posts normally activated ? what is the precursor for triggering it ?