If a new question addresses the same issue that another question does, but the answers to the original question is sufficiently outdated, should the new question still be closed as a duplicate?
Possibly. Depends on the situation. I would suggest posting a bounty to the original question and adding a comment that you are looking for more up to date answers (assuming the question wasn't full of comments and a lot of answers already).
If that answers are no longer good enough there must be a reason. Is it that you need better performance, has the base technology changed? If so add that to your question as a requirement to make it different than the original.
If the questions are duplicates, (not being a mod, i'm not entirely sure) but I think the answers can be merged so that they all appear under the one question. This sounds like it would fit your problem. If the new answers would benefit the old question then it seems like the best idea so that someone finding the question in the future can see all the answers.