There is to be no "necroing" of threads, which includes the following criteria: Bumping a thread that has not been posted on in over 2 weeks, unless the content of the thread has become relevant to be opened for discussion again. Bumping a thread that has not been posted on in over a week in order to flame, troll, or cause a problem.
Basically, if a thread has not been responded to in 2 weeks +, it is a "necro" thread. Even if you are on-topic, and posting your opinion, and you post after it has not been active, it gets locked.
Can I ask why is that you are so strict here about necro? I frequent some forums, and people are actually encouraged to dig up old threads and post new stuff they found about the topic, instead of posting new threads. Forum looks a lot cleaner and information is systematically stored and easy to access. Just wondering