Hi,
I'm not sure I understand your question sorry.
It lists new posts since your last visit as determined by your cookie and last activity on the server - so if your cookie expires before you finish reading the listed new posts then they would drop of the list and any refreshed page would only have those posted since that happened.
I think the cookie times out after 15 minutes of no activity.
To get around this you can keep this page open in one of the tabs - but even then it will eventually time out. This is because searches expire after a time and the new post is only a search by post time.
Does that explain things or just make them worse?
dr del