A. R. Orage's Readers and Writers (1917-1921) contains a rather intriguing piece on pp48-50 entitled "When Shall We Translate?" I will quote it rather liberally as it is not in copyright in the US or Japan (book published in 1922, author died in 1934).

There is nothing particularly "masterly" from the modern English point of view in Hobbes's translation of Pericles's Funeral Oration. His period of English prose appears to have been ill-adapted for the translation of the Greek idiom of the time of Pericles. To the usual cautions against translations in general, we ought to add the caution against translations made in dissimilar epochs. It is not at any time in the history of a language that a translation from a foreign language can safely be undertaken. In all probability, indeed, the proper period for translation is no longer in point of time, than the period within which the original itself was written. If the Periclean Age lasted, let us say, fifty years, it is within a period in English history of the same length that an adequate translation can be made. Once let that period go by, and a perfect translation will be for ever impossible. And equally the result will be a failure, if the translation is attempted before its time has come. I do not think that the Hobbesian period of English was in key with the period of Periclean Greek; nor, again, do I think that our period for perfect translation has yet come.

The idea that each generation should have its own translations is a pretty common one (if impractical for most source texts). The idea that only one or two generations can translate a given text properly is much rarer.

But I am confident that we are approaching the proper period, and in proof of this I would remark on the superiority of Jowett's translation over that of Hobbes. [...] Hobbes was a great pioneer, a creator of language; Jowett was only a good writer. Nevertheless, the idiom in which Jowett wrote, was more nearly perfect (that is, fully developed) English than the idiom in which Hobbes wrote. And since, in point of development, the correspondence between Periclean Greek and Jowett's English, is closer than the correspondence between Periclean Greek and Hobbes's English, Jowett's translation is nearer the original than Hobbes's.

However:

To a mere student of comparative values in Periclean Greek and idiomatic English, some of the errors in Jowett's translation are obvious. Such a student needs not to refer with the scholar's precision to the original Greek to be able, with the approval of all men of taste, to pronounce that such and such a phrase or word is most certainly not what may be called Periclean English. It stands to the totality of reason that it is not so. We may be certain, for instance, that Pericles, were he delivering his Oration in English, with all the taste and training he possessed as a Greek of his age, would never have employed such phrases as these: "commended the law-giver," "a worthy thing," "burial to the dead," "reputation ... imperilled on ... the eloquence," "who knows the facts," "suspect exaggeration." Pericles, we cannot but suppose, both from the man and his age, spoke with studied simplicity, that is to say, with perfect naturalness. The words and phrases he used were in all probability the most ordinary to the ear of the Athenian, and well within the limits of serious conversation. But such phrases as I have mentioned are not of the same English character; they are written, not spoken phrases, and approximate more to a leading commemorative article in The Times than to a speech we should all regard as excellent. It would be interesting to have Lord Rosebery's version of Pericles' speech, or even Mr. Asquith's. Both, it is probable, would be nearer the original than Jowett's, though still some distance off perfection. In another fifty years perfection will be reached.

I suppose "commended the law-giver" is unlikely to come up in regular conversation, but "a worthy thing"? "Who knows the facts"? ("Burial to the dead" sounds dubious, but it's actually just a non-constituent: "... given at their burial to the dead who have fallen ...")

Also note the lack of hedging in the final sentence. Not "may be reached," but "will be reached." By my calculations, this means that we English-speakers achieved Pericleity sometime in the 1970s — we don't have much time left before the period will be over and Pericles's Funeral Oration will never be properly translatable for us again. I hope someone struck while the iron was hot.

(I personally read Jowett's translation, apparently to my detriment, although looking through it now I still find it quite acceptable; "not riches, as some say, but honor is the delight of men when they are old and useless" has stuck with me since.)