It's high time to address the mega threads that is already filled with enough replies and nothing more to discuss about still people are commenting on the threads which leads to obvious spam so I feel we should lock those threads to encourage users to engage in the quality discussions rather than beating the dead horse. The number of pages/replies can be subjective, but anything past 10 pages has nothing to offer.
While I don't disagree the mega threads are awful, we need to first create the strong incentive for new topics, or which we have a dire quantity of new amounts (not enough to sustain having topics <10 pages). I suspect that locking topics with 10+ pages, if done so automatically as it were, would be locking half of the forum topics at present, and thus would likely only serve to half the number of active topics by default. New topics unfortunately do not create themselves, and locking megas won't create them either. Hopefully, once the
new initiative from President Freemind is properly initiated, the you initially proposed, of +karma for new topics and +karma for discovering them, then we can reconsider what to do about these old megas.