While reviewing in the Close Votes category, I've noticed that duplicates sometimes seem to have the duplicator and the duplicatee reversed. They suggest to close an old question with a good accepted answer, because there is a newer duplicate with no accepted answer.
I think that it's better and fairer to keep an older answer open, especially if it led to good and accepted answers. Also consider that the older answer probably has more views, and that someone who comes from Google might not think it's useful to click the 'might be a duplicate of ...' link if the answer he's looking for is not on the page where he landed.
So the suggestion is: give the reviewer the option Don't close this question, close the other one!
Here's an example
Original question, 2 years old, accepted answer, do I think this should be closed..
...because this 1 year old question without an accepted answer might be a dup?