Well crispyambulance said ~1000 years. That squiggly line means approximately, you can nitpick with him how approximate you want to be and which start and crumble dates you want to pick. Although he might point out that from the start of the Roman Republic to the dissolution of the Western Roman Empire gets you quite close to 1000 years (the overthrow of the 7th legendary king in 509BC; and Romulus Augustulus, the last emperor of Western Rome, up until 476 AD.)

Honestly this is a silly thing to nitpick, particularly when we all seem to agree that power structures can be virtually immortal on human timescales.