Quite often (especially on ArQAde, but also on other SE sites) new users post late answers to years-old questions that already have great upvoted answers. That's basically fine - except, these new answers basically only state what the others have already stated. In contrast to answers posted at almost the same time (see fastest-gun), in this situation there is practically no excuse for restating the accepted answer and it is most likely an attempt at rep-whoring or sheer laziness to first check existing answers (and there are usually not that many that skimming wouldn't reveal the similarity).
So, what's the correct behaviour towards these answers? Technically they are correct (and if they are phrased better than the existing answers they may even deserve an upvote), yet they basically bump an old solved question without adding any new helpful content and I'm actually tempted to down-vote them as I consider wasting everyone's time without reducing local entropy harmful. So, how to treat these answers?