Is there an exact date for when it's a thread necro?

Just as it says on the tin.
I expect there’s only really a rough idea as to when it would be.

No, I’d say it’s a judgment thing. The older the thread, the more your post ought to be relevant to the old discussion, and add something worthwhile. Bumping a somewhat old thread to say “yeah, cool” would be a total thread necro, but you could probably bump an even older thread to say “hey I’ve got this mod working again, here’s details and fixes for the above posters’ problems” and that’d be fine.

Ya, kinda figured it’d be kinda like that. I was largely asking out of curiosity on opinions and such.
Like I said, I figured there’d only really be a rough idea. Not super specific like ‘x’ months or whatever.

If you’re asking for what “feels” like thread necro, then I’d say that I tend to feel like “yeah, cool” is thread necro after 2 days of no other posts.

Normally, I would say that questions about gameplay that have already been discussed doesn’t count as thread necro ever, but with CDDA I would guess maybe resurrecting 6 month old posts is necro.

Also, use the tools the site gives you. If you’re reading an old thread and think, “hey this made me think of something similar”, don’t post a reply in that thread. Instead open a new thread, optionally with a link back to the old one.

Specifically, instead of clicking the reply button, click the :chains: “link” or “share” button and then click on + New Topic to make a new topic related to the old one. Please do this on not-that-old topics as well, it helps prevent derailing of discussions.