I stumbled upon an (admittedly old and) answered question on StackOverflow which I consider to have a better place here. Should and/or do we request migrations in such cases?
Generally old questions (especially ones with answers) stay where they are so as not to break people's bookmarks. It would suck if someone had a question that was answered on Stack Overflow, bookmarked it for future reference, and then comes back a few years down the road to find all the answers are gone and there's a big sign on the door saying "Go to this other site".
In this case the question is 3 years old - it's a good question but personally I'd let it stay where it is.
It seems happy :)