There's not really a need to get rid of older questions unless they have some underlying problem. Facts will remain facts forever, and we require authors to write questions that are not time dependent. In the past, this may have slipped through a bit more often. But that's one reason we have the correction system! We can keep these quizzes online as long as we fix any issues with them.
Trust me, there have likely been thousands of past quizzes pulled offline for various issues. One thing that players may not know is that one of the many tasks of the editors is to go through these offline quizzes, check to see if they are salvageable, and if they are, fix them up to go back online. The more questions we can keep in the database, the less you will see repeats in the various games.
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Perception is everything.
Editor: World, History, and General