How long did the Athens empire last?

Answer 1

Athens never had an empire; Athens was a city-state. The Greeks themselves never had an empire. They were a collection of city-states, each with its own laws, religious rites, surrounding territories and allied cities. The closest the Greeks came to an empire was with the conquests of Alexander the great, but even his territories did not meet the criteria of an empire and it fell apart at his death. The various Greek city-states, when not fighting each other, did unite against a common enemy, such as the Persians, but when the hostilities were over the unity was over and the various fighters/leaders returned to their own cities and went on with their separate lives.