Julie, unfortunately, yes. If you log in, you need to check / read them in one sitting, or they won't be marked as new anymore after two hours have gone by and your browser session hasn't had any contact with the server.

On the bright side though, even though "New Posts" may come up empty, you can still look at the icon at the left of each post. Threads you've replied to will have an arrow going through the icon. I know this won't help on posts to which you've already replied, but it'll at least give a clue about the things you haven't responded to at all.

The major update has been on the "we're working on it as fast as we can" list for a while now, so I imagine they're going to come out with it soon. When it's here, I'll post back.