I am aware of this similar question on Meta Stack Overflow, but it mostly deals with duplicate answers that come about due to the race to answer, which is outside of the scope of my question (which deals with answers made a lengthy period afterwards).
I have, in the past, flagged answers that are merely a subset of the same information contained within a previous answer, where the two answers were not both posted within a reasonable timeframe of each other.
Previously this has not been a problem, and my flags under this context were approved, but yesterday I had a flag of this type declined as being on principle not suitable for the flagging system.
Is appropriate to flag answers that are merely repeating the same information given a significant time previously, and, by which, add nothing new? If not, are answers that are merely repetitions of previously given information considered a non-issue?