Is it possible to add a closing reason which is along the vein of "No longer relevant"?
Such reason would be very useful for big-lists (which are not frowned upon here) when they become too big (i.e. when users begin to duplicate answers).
Edit: If you have a better closing reason for which we can ask the StackOverlords for, please post it as an answer (one reason per answer please).
Edit 2: I agree that it might be not-very-useful everyday closing reason, but it would be a good option to know that the moderators can close something under this reason. In a recent example, Are there real-life relations which are symmetric and reflexive but not transitive? (also see this) the question was reasonably closed, but with lack of closing reason it was closed for being non-constructive which would be an inaccurate reason to close it.
If the moderators could cast closing reason outside the scope of normal users then a moderator (in this case, Zev) could have closed it for one reason or another which may have been better suited for the question.
The same reasoning is applicable in other questions which become too big to be useful to anyone who hasn't followed them from the start.