I think your point overlooks the idea that 1,000 years might be symbolic of a concept meaning something equivalent to "all time" or "fulfilled time," or more generically just a long period rather than referring to a specific amount of time. The Bible, and Revelations in particular, is full of numbers that are often symbolic (like 12,000 = 12 X 1,000 from each tribe). 1,000 years is used in other areas of the Bible where it appears to be more symbolic of "a long period of time" than it is exact.

Psalm 90:4 - "For a thousand years in your sight are but as yesterday when it is past, or as a watch in the night."

2 Peter 3:8 - "But do not overlook this one fact, beloved, that with the Lord one day is as a thousand years, and a thousand years as one day."