When and how do mature [faq-proposed] posts graduate to [faq]?

On a per-site Meta, it's really up to the moderators to add the faq tag to questions they think are worthy of them, but since I've been in the process of cleaning these up (slowly over time) over on the main Meta, I've also been curating some criteria I look for when determining whether something is worthy of being a FAQ or not, so I'll share them here.

• Number of answers. You might not think it, but it's hugely important. Unless there's just plain too much information to fit into a single answer, a FAQ simply should not have more than one answer. If it has more than one answer, then it should be edited so that all the information is contained in a single answer in a way that portrays the information accurately without elements of discussion or opinion. If that cannot be done, then the topic either hasn't reached a stage where the community can provide a definitive answer, or it's too open-ended to really be a FAQ anyways.

  To expand on this further, users don't search for FAQs to read a discussion on a topic. If they wanted to see a discussion, they can look at a huge array of other questions surrounding that topic. Users go to a FAQ because they want a definitive answer. They're curious about something and want to know the hard facts. If we can't provide that in the question, then we shouldn't advertise it as such.

  These situations often pop up when a large discussion has taken place and the community has reached a consensus. The easiest thing to do is to just slap a faq tag on that question and call it good. NO. A much better solution is to create a new question which outlines the policies the community decided should stand. Again, definitive information without discussion.

  Leaving a FAQ sit around with all the discussion still behind it leads users to become confused, as it makes it look like the community hasn't really decided what the policy is, and all that information in the question has simply become words on a page. They're left with the feeling of "so, is this policy or just someone's opinion?"

• Number of views. Well, part of the acronym of FAQ is the word "frequently" - which implies it comes up a lot. If the question is rarely ever collecting views and no one is looking at it, then it is not coming up often enough to warrant the additional attention that a FAQ tag provides. The FAQ index should be kept clean and only contain relevant topics users are actually trying to find - we should avoid cluttering it with links to topics no one cares about.

  A lot of duplicate closures pointing back to the FAQ itself is also a pretty strong indicator that users are looking for this information often.

• Information display. Perhaps the biggest reason we start questions as proposed FAQs is because the first draft usually isn't the best way to display information to the user. It's just that, a first draft. Most proposed FAQs require much additional curating to provide proper formatting, separate information into understandable sections, make everything crystal clear, and overall make the exact piece of information a user wants to find - easy to find. If the entire answer looks like a book with paragraph after paragraph and no discernible way to find more relevant pieces of information, then it's definitely not ready.

As far as adhering to the FAQ standards, that's easily fixable with a couple of edits, and isn't something to be considered past "oh that needs to be done if I make this a FAQ." All the other factors you mention aren't really good factors for determining FAQ worthiness.

These are far from definite criteria, and I've kind of put processing these on hold for now as other things have come up and I'm exploring other options regarding this whole mess of FAQs that's becoming way too large to organize properly.