Did you see Zionist Conspirator's thread on this very subject last week? Worth reading IMO.
Thank you so much for the link! It is indeed a very interesting subject.
The theology of a 7,000 year limit of Adamic man on earth (with the last 1,000 years being Christs reign on earth) is based on the seven days of Creation in Genesis as applied to these verses and Revelation 20:
But, beloved, be not ignorant of this one thing, that one day [is] with the Lord as a thousand years, and a thousand years as one day. 2 Peter 3:8
The 7000 limit for Adamic man is also a traditional understanding of time in Orthodox Judaism. I have not yet read San Hedrin 97b, but I understand it contains a reference to that very point.
Pseudepigraphral manuscripts explicitly make the connection, most notably Enoch 2 and the epistle of Barnabas 15:1-5.
Of the Sabbath He speaketh in the beginning of the creation; And God made the works of His hands in six days, and He ended on the seventh day, and rested on it, and He hallowed it.
Give heed, children, what this meaneth; He ended in six days. He meaneth this, that in six thousand years the Lord shall bring all things to an end; for the day with Him signifyeth a thousand years; and this He himself beareth me witness, saying; Behold, the day of the Lord shall be as a thousand years. Therefore, children, in six days, that is in six thousand years, everything shall come to an end.
And He rested on the seventh day. this He meaneth; when His Son shall come, and shall abolish the time of the Lawless One, and shall judge the ungodly, and shall change the sun and the moon and the stars, then shall he truly rest on the seventh day. Barnabas 15:1-5
I said to him: Earth you are, and into the earth whence I took you you shalt go, and I will not ruin you, but send you whence I took you. Then I can again receive you at My second presence.
And I blessed all my creatures visible and invisible. And Adam was five and half hours in paradise. And I blessed the seventh day, which is the Sabbath, on which he rested from all his works.
And I appointed the eighth day also, that the eighth day should be the first-created after my work, and that the first seven revolve in the form of the seventh thousand, and that at the beginning of the eighth thousand there should be a time of not-counting, endless, with neither years nor months nor weeks nor days nor hours.
And now, Enoch, all that I have told you, all that you have understood, all that you have seen of heavenly things, all that you have seen on earth, and all that I have written in books by my great wisdom, all these things I have devised and created from the uppermost foundation to the lower and to the end, and there is no counsellor nor inheritor to my creations.
I am self-eternal, not made with hands, and without change - Enoch 2 32 and 33:1-3