It appears that if an question has been asked before, the policy is to mark it as duplication. This makes sense in cases where there is a definite and absolute answer, but I can think of two instances where this model breaks down:
when the answer is time sensitive – for example, when recommending a plugin/gem to solve an issue, newer solutions become available, and the old answers become irrelevant.
when the question's main purpose is to generate relevant discussion, and the old thread is stale – the main purpose of stackoverflow sites is to answer questions, but the value (at least to me) is the community. Relegating discussions to an dead archive, just because they've been had before, lessens the value of stackoverflow.
I request you consider revising your
mark as duplicate policy for these two instances.