What are the policies/general guidelines on thread necromancy?

[TwoHundredTabs]

I'm looking at some threads and thinking to myself "Well, there don't seem to be any posts here that would generate conflict if I bumped the thread up to the top of the list with my post..." and "It makes sense to just add on to what has been said here, because I agree with a lot of it and/or it's well-developed thought."

Soo.. are there any rules-of-thumb we can follow for when it's ok to post in a thread older than 120 days?

[Oreo]

So long as the topic is still relevant or currently news worthy it is most likely okay to post. Things tend to slide back down to the bottom of the pile as the site is quick paced. In the fun games/socializing there shouldn't be a problem. The one thing we do frown upon is bumping for the sake of bumping.

[Oniya]

A rule of thumb that I use (which is by no means an official site policy) is whether I am adding to the topic, or just posting an 'I agree.' 

[TwoHundredTabs]

A rule of thumb that I use (which is by no means an official site policy) is whether I am adding to the topic, or just posting an 'I agree.'

Yeah, I think that's the most important thing to consider. In cases where relevance/newsworthiness is less clear, I'd make my decision based on whether or not I thought that my post would contribute something new and meaningful to the discussion. And, as I mentioned in the OP, I wouldn't add to topics likely to re-start old conflicts.

If I thought that making any post - whether as a reply or as a new thread - might cause conflict, I'd weigh (1) how important I thought the post was and (2) how many people I thought would be impacted by/interested in it, against (1) the likelihood that the topic would be upsetting to people [e.g. due to personal beliefs or past experiences], (2) the likelihood that the topic would be too controversial, and (3) the likelihood that arguments would dominate the thread.