Deuteronomy 11:21 ESV that your days and the days of your children may be multiplied in the land that the Lord swore to your fathers to give them, as long as the heavens are above the earth.
land- H127 אֲדָמָה ‘ădâmâh- soil (from its general redness): - country, earth, ground, husband [-man] (-ry), land.
earth- H776 אֶרֶץ ‘erets From an unused root probably meaning to be firm; the earth (at large, or partitively a land): - X common, country, earth, field, ground, land, X nations, way, + wilderness, world.
above- H5921 עַל ‛al Properly the same as [H5920- properly the top; specifically the Highest (that is, God); also (adverbially) aloft, to Jehovah: - above, high, most High.] used as a preposition (in the singular or plural, often with prefix, or as conjugation with a particle following); above, over, upon, or against (yet always in this last relation with a downward aspect) in a great variety of applications: - above, according to (-ly), after, (as) against, among, and, as, at, because of, beside (the rest of), between, beyond the time, both and, by (reason of), had the charge of, concerning for, in (that), (forth, out) of, (from) (off), (up-) on, over, than, through (-out), to, touching, with.
Eretz can mean either the land of Yisroel, another ‘land,’ land as opposed to sea, the entire earth … . But interesting here instead of eretz the verse first uses adamah, which specifically means earth as in soil: dirt. So contextually, and given the relation to H5920 it more likely (my opinion) would be translated as the ESV does, “as long as the heavens are above the earth.”
However none of the options can be ruled out completely, and there may be good lessons to be learned from each translation.
Can our days be multiplied as the days of the heavens upon the earth? If this be true then it is doubtful that this occurs in the natural and physical just because of the physical land wherein we reside.
What if this speaks of the kingdom of the heavens? (Matthew 8:11). Is it possible in this life to sit down with father Abraham, and Yitzhak, and Yakob, and all the Prophets, (which would include Mosheh), in the kingdom of Elohim? (Luke 13:28-29).
Matthew 8:11 I tell you, many will come from east and west and recline at table with Abraham, Isaac, and Jacob in the kingdom of heaven,
Luke 13:28-29 In that place there will be weeping and gnashing of teeth, when you see Abraham and Isaac and Jacob and all the prophets in the kingdom of God but you yourselves cast out. And people will come from east and west, and from north and south, and recline at table in the kingdom of God.
These things will occur at the end of days, not in our present lifetimes. But if I read Revelation right, the Kingdom of Heaven will come to earth as well, and God will reign here as well as in the heavens.
“As long as the heavens are above the earth” makes the most sense to me though, as in the end (the kingdom of) heaven will come down to earth.
Revelation 21:2-3 And I saw the holy city, new Jerusalem, coming down out of heaven from God, prepared as a bride adorned for her husband. And I heard a loud voice from the throne saying, “Behold, the dwelling place [tabernacle] of God is with man. He will dwell with them, and they will be his people, and God himself will be with them as their God.