That depends with the discussion.
Recently someone create a thread which is better gold or Bitcoin, such discussion has been discussed multiple times and I don't see any reason why people have to discuss it now.
But, if someone create a thread to discuss about his own analysis and state which is better between two to invest in this year, he deserve to create a new thread because he talk about in specific period instead of talk in general.
In examples like this where the topic is almost an exact match, I think that the threads should be merged.
Otherwise I agree with Dread:
I think forums should generally let new discussions happen even on repeated topics. When you lock threads just because "we already talked about this," you kill the community vibe.
Tech and crypto change so fast - last year's Bitcoin discussion is already outdated. Plus, new members bring fresh perspectives that would be lost if we always redirected to old threads.
Instead of shutting conversations down, maybe just link to previous discussions while letting the new one continue. This gives context without stifling engagement.
The best forums feel alive with conversation. A bit of topic overlap is worth it if it keeps people talking and sharing ideas. After all, forums are about community, not just being a perfect archive.