That your days may be multiplied, and the days of your children, in the land which the LORD sware unto your fathers to give them, as the days of heaven upon the earth. Deuteronomy 11:21
Some churches hate the idea of a literal, thousand year period when righteousness reigns upon the earth. They demand that it be interpreted as indefinite and that it began either at the crucifixion or at Pentecost. They hate the idea of a literal 1,000 year period because it has been almost 2,000 years since these events, and we certainly do not live in a righteous world.
I debated such an objecter to literalism. He said that since the Bible says "He owns the cattle on a thousand hills", and since God owns more cattle than that, "thousand" is not literal. This is a typical low-level arguing technique. If you can find one place where a word is used non literally, than it can never be literal.
There is a perfect Biblical definition of the millennium. It is the time when Satan is bound.
And he laid hold on the dragon, that old serpent, which is the Devil, and Satan, and bound him a thousand years, Revelation 20:2
Is Satan bound today? Then this is not the millennium.
Once Satan is bound there will be a shower of blessings upon the earth. These blessings will be for Israel and those who follow her.
Eternal life is not in view, just very long lives, as in the beginning. Earth cannot go to heaven, but heaven's blessings can come down to the earth.