I think the title speaks for itself. Several times I have come across old questions with some interesting information in answers, sometimes with highly upvoted and/or accepted answers, but by the letter of the help center, they are off-topic.
Not all of these "old" questions are even all that old. Some are only a couple years old. Obviously there are some venerable questions from the earliest days where even the current scope might not yet have been fully refined.
So that brings up the secondary question of whether how old a question is matters in terms of closing or flagging it.
So what should we do in these situations?