I generally think new posts are a good idea. The old post is what it was when it was written. If you no longer endorse it or think you can write a better version, do so and link it from the original. I think there is value in being able to find and read old versions of things as they were when they were written without the past being edited out of existence, letting us see the trail of how an idea was shaped and formed and how the author grew in their understanding and ability to express themselves. Additionally the comments on a post may no longer make sense if you substantially edit it.
I generally think new posts are a good idea. The old post is what it was when it was written. If you no longer endorse it or think you can write a better version, do so and link it from the original. I think there is value in being able to find and read old versions of things as they were when they were written without the past being edited out of existence, letting us see the trail of how an idea was shaped and formed and how the author grew in their understanding and ability to express themselves. Additionally the comments on a post may no longer make sense if you substantially edit it.