This is where I am at. The notion that HN posts die off relatively quickly (i.e. within ~48h) is potentially a very important part of what gives them the quality they have today.
If every post was eternal and duplicates were always closed, you'd wind up with effectively perma-stickied comments in these god threads that become the law for that topic until the end of time.
You could have an AI to summarize the last N comments, giving an overview on the most recent opinion.
I do this informally: https://hn.algolia.com/?dateRange=all&page=0&prefix=true&que..., but that's all just prep for one day fitting it nicely into the software.
For example, are all the various ChatGPT threads related? What about coverage of an event (e.g. there are six or seven threads regarding the recent earthquake in Turkiye—all empty apart from https://news.ycombinator.com/item?id=34672314 —however I've seen it where basically the same story is being carried across several outlets and discussions are on the same topics, just one post gets more traction than the other).
It's easy enough to link articles which refer to the same exact source and mark duplicates, but harder to link posts which rely on different sources to cover the exact same topic.
A lot of projects get posted and there's a reply that mentions the 2 or 3 other times in the past it was posted, with links to the comments. I thinks that's one way to deal with longer term topics and updates--allow reposts over time and new discussion, with links to the past discussions if folks are curious to dig deeper into the history.
IMHO not much really needs to change, I think how reposts and such are handled right now is great.