There are the obvious ones like giveaways, but some old threads are still very valid today.
Personally, I’d put a little more pressure on cleaning posts out (and not letting people derail so badly). As an example, just now I went through the MF Recommendations and it’s just horrible… that thread should be split up in 4 or 5 separate threads. It’s a very painful exercise to extract the information for which people open the thread. Not sure where the guidelines are scattered anymore, but I read somewhere that people should only post into a topic if they can contribute to the ongoing topic (otherwise start a new thread or continue in a more appropriate thread). I don’t give a hoot about what people just ordered and what samples they got when I’m browsing for recommendations.
I don’t often come across a thread that I think should be closed (few exceptions, especially the threads that contain a lot of bashing, they extract the worst out of some people… but the mods are usually doing a fine job to keep stuff in line).
Expired codes or whatever can be flagged for attention and perhaps removed when they’re (confirmed) not valid anymore.
The question is, what is “old material” and where do you draw the line. With an expired coupon code it’s easy but not everything is so black and white. Even older recommendations for hardware may still be valid if you can still buy it (even used).
@Ken_O_Where imo derailment is still the biggest issue that needs a solid solution. I would just stick a big fat derail button next to the reply button, something that takes people to a safer place to wander off into the abyss.