I have been told, that since "thousand years" is mentioned 6 times, it must be taken literally.

And I do believe that the thousand years are to be taken literally:

Revelation 20:2 And he laid hold on the dragon, that old serpent, which is the Devil, and Satan, and bound him a thousand years,

  3 And cast him into the bottomless pit, and shut him up, and set a seal upon him, that he should deceive the nations no more, till the thousand years should be fulfilled: and after that he must be loosed a little season.

  4 And I saw thrones, and they sat upon them, and judgment was given unto them: and I saw the souls of them that were beheaded for the witness of Jesus, and for the word of God, and which had not worshipped the beast, neither his image, neither had received his mark upon their foreheads, or in their hands; and they lived and reigned with Christ a thousand years.

  5 But the rest of the dead lived not again until the thousand years were finished. This is the first resurrection.

  6 Blessed and holy is he that hath part in the first resurrection: on such the second death hath no power, but they shall be priests of God and of Christ, and shall reign with him a thousand years.

  7 And when the thousand years are expired, Satan shall be loosed out of his prison,

However, I have also been told, that since "thousand generations" is only mentioned 3 times, that it should be taken figuratively.

i.e. I've been told that a thousand generations does not literally mean a thousand generations, but only indicates a long time.

Deuteronomy 7:9 Know therefore that the LORD thy God, he is God, the faithful God, which keepeth covenant and mercy with them that love him and keep his commandments to a thousand generations;

I Chronicles 16:15 Be ye mindful always of his covenant; the word which he commanded to a thousand generations;

Psalms 105:8 He hath remembered his covenant for ever, the word which he commanded to a thousand generations.

However, is that not the same thing that amillennialists say about the thousand years in Revelation chapter 20?

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