My take on this is always to never remove or deface old answers or workflows.
They may always help people that for one reason or another are stuck with older versions of Blender. Say support old hardware, LTS versions, finishing an old project part of a larger studio pipeline, or if something breaks on newer versions beyond reasonable efforts to repair. At the very least they may be historically relevant, maybe as a reminder how (hard or convoluted) things were before.
First attempt should always be to update existing answers to reflect changes. Insert additional screenshots, add a line describing the new menu structure or shelf where it can be found, etc. without removing the old ones.
If this is unpractical, like say changes to the workflow were significant enough that an answer would be hard to follow if it tries to cover multiple versions, there are more than two possible workflows for different releases, or a completely new (or deprecated) feature changes the fundamental way to go about it, then post a new answer.
Last resort would be to post an entirely new question and answer it there. Having a new answer in an older well established post helps for a few reasons.
It reduces information scattering. By having all possible solutions in a single post makes them easier to find. From the point of view of a user looking for answers, it is also easier to have a single long list of solutions than to jump around a multitude of tangentially related posts that are easy to miss.
One of the biggest hurdles of people pointing new users to duplicates is finding the actual duplicates. To the extreme that more often than not it is easier to just type a new answer than to look for that darn old duplicate. Stack exchange search isn't always the best either, and finding relevant answers potentially worded differently can be hard even for veterans, let alone for new users.
A single well written and comprehensive post is easier to follow than ten superficial ones scattered all over. Updating a single one in the future is also a lot less maintenance work then keeping ten posts relevant when there is a change.
Having all answers in a single post makes it more comprehensive, more memorable and easier to go back to. It also helps people who deal with review queues, making the canonical post used more often and hence easier to remember. Gaining more votes also gives people looking at it more confidence.
Conversely having different questions with multiple answers each for the same problem makes it all the harder to dealt with. For these reasons I would urge anyone posting an updated answer to an old problem to prefer doing so in an original "canonical" question.
I understand this is less appealing for users trying to build reputation, and get their hard earned points for their efforts. Earning points these days is hard enough as it is, and answering in some dusty question of yore makes it even less visible.
All the while the new and updated answer, that is arguably more desirable, is pushed down the list and made less visible, since it hasn't yet gained as much points compared to the old and tried one. Maybe it never will.
For that I don't have an easy solution and would like to hear the opinion rest of the community.
If the price to pay for that is having duplicate answers then let it be so. Post your new and shiny answer in two places, the newer question for points (or at least a "lite" simplified or summarized version of it, pointing to the older more complete question for more details), and a full version of it "for future reference" in the canonical post, complete with all the details where it would ideally gather more points in the long term.
Again this is my take on it, that definitely has its shortcomings like duplicate answers, data buildup, and extra work for the poster which can be discouraging, and maintenance work enforcing it.
Lets hear what others have to say about this, looking for better solutions.
