So many great topics here (both new and old), but would be nice to know if past topics are still open for posting.
As long as you have something relevant to add to the thread, it should be OK, depending on the forum. In General Questions, you should provide something factual. In other forums, a relevant opinion or piece of information should be acceptable. Drive-by comments should be avoided.
Sure.
But you may want to preface it by acknowledging that it’s an old thread:
“I know this is an thread but just wanted to add/update that…”
What you don’t want to do is jump into an thread from 2005 to give your opinion on someone else’s opinion expecting an immediate response from somebody who isn’t around anymore or totally forgot what they were talking about 15 years ago.
Yes, in most cases. If you want to dig up an old thread on Shakespeare and add your comments, that’s fine.
I’d avoid some of the more personal threads from years ago. Even if you’re being sympathetic, I wouldn’t dig up, ‘My wife died today’ ‘My son committed suicide’ or ‘I’m getting a divorce’ type threads from years ago. Yes, they’re still on the SDMB, but no need to resurrect them.
“Yes, in most cases. If you want to dig up…Shakespeare…I wouldn’t dig up, ‘My wife died today’ ‘My son committed suicide’…no need to resurrect them.”
Hmmm. Isn’t that what digging up would be? 
Is this the end of zombie Shakespeare?
Moderator Action
Moving thread from IMHO to ATMB.
There’s no rule against resurrecting old threads, but it is generally frowned upon unless you have something significant to contribute to the topic. People tend to refer to old threads that have been resurrected as “zombies”, so if you don’t add anything significant, then most likely you’ll just get a bunch of zombie jokes.
The older the thread is, the more likely it is that many of the original thread participants are no longer around to see any comments that you make.
The General Questions forum in particular is significantly less tolerant of zombie threads than other forums. Since GQ is a factual forum, we ask that you do not raise old threads in that forum unless you have something significant and factual to contribute.
If you do have something significant to contribute to the old thread, you don’t necessarily have to resurrect the old thread. Another option is to start a new thread and link back to the old thread. This is the better choice when your comment is more likely to spawn a new discussion of the same topic instead of just adding to the old topic.
If you have a question about a specific thread, feel free to PM the moderators of that forum and ask them if it is better to post to that thread, start a new thread, or if it’s better not to post it at all.
We had an example in CS recently, where someone over a decade ago made a thread about “There was this film I vaguely remember, but I’m not sure what it was”. A couple of days ago, it got bumped by the film’s director, filling in all the details the OP couldn’t remember. Everyone involved thought that was pretty cool.
That is pretty cool. Does anyone have a link?
An extended thank you to all for replying.
Here is the most recent thread in Johnny L.A.'s quest to find the short film 20 Mile Limit, which includes a visit from the director.
Agreed. Please don’t keep opening old zombie threads unless you have something new and relevant worth reviving it for. Feel free to start a new thread in Mundane Pointless Stuff I Must Share.
The SDMB has been around for quite a while, and most threads nowadays are repeats of what’s been said in the past. If you want to be sneaky, use those old threads to post meaningfully in the new ones. I’ve never done it intentionally, but I have thought that some of my input might echo what’s in those old threads.
ETA: If you’re interested, there’s a sticky thread on how to Google the Dope.
IMO, I don’t see why it would be a problem.
Bear in mind that’s its disconcerting to see a 12-year-old thread revivified just so Polyester can once again reminisce about baby diapers or some such, only to see that it’s filled with posters who are no longer on the board and deceased. All her postings have been drive-by’s with no new information, just “I like changing diapers, too” and the like. Just start a new thread if you have something to say.
Yup. I even told her to avoid making drive-by comments.
Im glad to know this engineer cause often I scan the bases for good threads to reply to and if I found one and the link was still valid (if any) I would reply rather than start a new thread because it looks better than having multiple threads on the same topic all over the site…
Even if the thread started has moved on and doesnt see it,doesnt mean others wont benefit from it 
We’re like the Talmud. A really good reply overrides the time difference!
Most of the time, when I do it, I don’t notice it’s an old thread. Someone will say "Here’s a fun take on Underdog!"and link to it, I’ll open it up, add my Underdog/Wally Cox/Power Pills theory, and two days later realize “Oops, it’s an accident!”
Except for this thread. I’ve set an alarm for Oct. 12, 2022 to comment on Horatio’s Talmud line…