Unfortunately, in between visits, its easy to miss a few hundred posts - because the forum software isn't able to tell a member which posts they haven't viewed yet.
I'm a little confused by this remark, when you're logged in you don't get the little "new" icons like this:
If I click on those icons I get taken to the new posts in that thread.
I've found this forum software to have much more reliable new-post tracking than, for example, the software on avrfreaks which always seems to get confused about new posts.
--Phil.