Recently, I accidentally posted a question on Stack Overflow, when I actually intended to post it on superuser.com (where it would almost certainly have been useful and relevant). The question was closed. However, the question is now too old to migrate, and I am concerned that it may leave this question open to the risk of deletion, no matter how potentially useful it may be.
Much to my dismay, I recently learned that popular off-topic questions on Stack Overflow are being routinely deleted, and I'm concerned that some of my own questions may be affected by this process as well, no matter how popular or useful they may be.
Will useful (but off-topic) questions like this one be saved from deletion, and is there anything that I can do to prevent this particular question from being deleted, so that I won't lose the useful information that I have gained from it?