Forums have a universal issue of people resurrecting threads that have little to no relevance months after they were originally posted. This is especially the case since the meta changes If possible, these threads should be autolocked after 2 weeks.
Forum posts should be allowed to cross reference and link old posts if necessary in the rare occasion that an old post needs to be quoted to emphasize a point or an idea. However, this is not a core issue as topics change as fast as the meta and expansion releases and quickly becomes irrelevant when new updates occur.