It's literal, ending about 1054 A.D.
The idea of a literal 1,000 year millennium originated from Jewish ideas regarding 7,000 years of human history. Two views (both are wrong)...
Christian millennialists borrowed option 2 for their 1,000 year yet-future utopian millennium. But modern millennialists usually increase the 6,000 years to 10,000 years or more because their view of young earth creationism demands a creation date long before 4,000 B.C.
Chiliasm (millennialism) as understood by a small minority of the early church fathers is based on this Jewish model of human history but is radically different than modern Christian millennialism. If modern Christians believed what these early church fathers believed they would be run out of church.
Even though the early church fathers consistently based their end-time views on this 6,000 year model, there is no hint of this thinking in the New Testament. All we know of is the expectation of a Messiah.
Many uses of the word "1,000" in the Old Testament clearly refer to an exact number (exactly 1,000) or a round number (approximately 1,000).
Others are clearly intended as figurative with the meaning of "all," "forever," "many," or "abundantly". A few examples...
A little math proves 1,000 is not literal.
Assume it's literal: a generation = 20 years, giving 20,000 years in which God remembers his covenant. But this contradicts: the word "forever" means the same as "1,000 generations", so "1,000" means "forever".
God owns all the cattle on all the hills
This passage doesn't limit God's blessing to exactly 1,000 times; rather, it means God is the source of "all" increase and "all" blessing.
People have never lived 2,000 years so it's figurative.
The word "1,000" is means a large number.
A key verse used to "prove" millennialism...
1,000 years (a long time for us) is like a day to God
So it's not...
1 day (of Genesis creation) = 1,000 years (of world history)
1,000 years (of human time) = 1 day (to God)
Even worse, millennialists don't claim that creation occurred about 4,000 B.C. yet this interpretation demands it. You can't halfway use the formula...
1 day = 1,000 years
without also using the formula...
6 days = 6,000 years
Similar to previous.
Satan was bound in the abyss where he could not deceive the nations nor could he corrupt the gospel, otherwise he could have destroyed Christianity. But after his release, Christian doctrine was too entrenched to ever be destroyed, although he continues to try.
Loosed a little season — from about 1054 A.D. to the end of the world occurring perhaps hundreds, or thousands, or millions of years from now. It might seem the phrase "little season" demands fulfillment within a decade or two but remember, Satan has been at his corrupting of the creatures of the world for 4+ billion years.
Perhaps Satan is not able to destroy the gospel message now because it is dispersed, similar to God's confusing of languages to disperse their power so they don't form a global government. The key ingredient of the great schism of 1054 A.D. was a permanent division between eastern and western Christianity.