"Empire" is really just a large hereditary monarchy with the ability to subordinate nearby ethnic groups into a unified political/military command. They can be remarkably stable. China managed two to three thousand years, depending on whether you want to count Zhou (pre-Qin unification) or not. I suspect in another millenium the Chinese empire historians will gloss over the discontinuous period of the 20th century ("nuclear glass layer era") and claim four thousand years.

Didn't the Roman Empire last nearly 1,500 years in one form or another?