The Mauryan empire ruled for 137 years, from 322-185 B.C. They ruled for such a long time because they had a strong, organized government. They ruled harshly and gave the subjects no choice of talking behind their backs. Since the Mauryan empire had such a harsh way of ruling they were famous for their secret polices (they would "take care" of all who bad-mouthed their ruler), and harsh rules.

How long did the Mauryan Empire rule for?

http://en.wikipedia.org/wiki/War_elephant