First off, forgive me if this has been proposed already. I did not find anything in the search, but of course I didn't search every suggestion there is.
In some SO questions (and I'm sure SF/SU as well), you will come across a nice practice: The asker will update their question frequently to adapt it to the answers given and discussion occurred, making the question itself a valuable resource. Let me point to a question of my own as an example. There are many, many others maintained with equal or more care, but I had great fun with this question and that kind of underlines my point.
This, of course, works best for questions whose answers can be compiled into a list ("what good x are there for platform y with technology z?"), but in essence, it applies to any question where the asker puts extra care into making the question a understandable, well-formatted resource that is helpful to somebody who comes across the question later.
The flow of questions on the trilogy of sites is always linear. Duplicates will sometimes be linked to older, already answered questions, but they might just as well be answered anew, because the duplicate can't be found or isn't searched for. The result is that probably most of the questions that have been asked are present multiple times, with answers that naturally differ in quality.
Now I realize this is in the basic nature of Q&A sites. Still, I would like to see a possibility and systemic encouragement to groom and update selected "worthy" questions (and their answers) beyond a few days after it has been asked. For the purposes of this proposal, for want of a better fitting word, I will call them "groomed" questions.
What I would like to submit for discussion is the idea of adding incentives for askers to take care of such questions, and update them if new information comes in, making them valuable long-term resources.
To create a new category or special tag for "groomed" questions.
To give "groomed" questions some sort of visual preference when listing to point out that this is a question meant to be a ongoing, updated reference or list.
To list these questions in a separate area in the user's profile.
Potential up sides for SO and users:
A "groomed" question would be the reference link when pointing out that a question is a duplicate
Would be in accord with what I understand is SO's mission statement: To become a knowledge resource for all programming related questions
Could add incentive for users to outsource parts of their own knowledge base to SO, gaining recognition and corrections / criticism / feedback
Would increase the overall quality of the data base
Linking to a "groomed" question is more likely to happen than a years-old answer
Maintaining the information amassed in a SO question is hard work as well, and a list of well-maintained questions visible in the profile would become a user incentive in itself
Potential cons and down sides:
The biggest down side I can see is that attention - and probably the better part of long-term upvotes - would be shifted from the answers (whose authors do the main work, and provide their knowledge) unjustly to the question and the asker. This would lead to the asker being rewarded (by upvotes) for repeating the findings the answerers have gathered. This would have to be addressed in a way that serves both the answerers, and the asker. I don't think Reputation will be the reason for people to take extra care of your questions, but it is the most basic expression of approval and acknowledgement from the community, and as such, important.
This question asks about more incentive for editing, and its accepted answer is that there is enough incentive to edit as it is.
Note that I am not talking about turning SO into a site of static FAQ pages. What I mean is adding the possibility to give some questions a faq`ish touch without changing the basic way how things work.