I can see both sides. On one hand, old threads are indeed a goldmine of information. So, I think the "Recommended Reading" list at the bottom of the new page view is really useful. It probably keeps people from asking the same questions over and over.
On the other hand, it also gets really annoying to see people (usually brand new members) "reply" to someone who hasn't posted for years. I'm waiting for the sad day when some knucklehead replies and gives "advice" to one of our dearly departed RF members who has passed away.
If the software could be tweaked, I think the perfect solution would be to have a banner come up when someone is replying to an post over "X" number of months, and the mods could set "X" as whatever they want. Right now the forum pops up a warning banner if "new posts" have been submitted since I started typing a reply. If the software is sophisticated enough to do that, it should possible to code it to say something like, "You are replying to a thread that has been inactive for more than twelve months. You may wish to consider starting a new conversation."