Well, the top section of the front page News is really for significant updates. If you scroll down a bit you can see the less important 'Developer Updates' and 'Patch Notes' below which have been updated more frequently. Significant updates for the top News will be coming once I'm done with this current optimization phase that I've been working on.
Regarding old forum posts... I wonder if you have forums set to display posts by some setting (poster, alphabetically) other than by recent date. The most recent posts should show up on the first page of each sub forum. If you're seeing very old posts on the first page of a specific forum, please let me know which forum. There are default settings for the order of posts and depending on when you created your account here, the settings may be different.
As for old posts not on the first page of each sub forum, I do clean out some old posts from time to time. However, I'm not very concerned with posts several pages deep as only a very tiny percent of people will look through those pages. Spiders do loop through and index those pages though, so in cases where posts have good keywords, it helps boost the site's Google (and other) rankings.
Thanks!