Congressmen currently have the ability to serve an unlimited amount of terms in the United States. Unless they do something severely wrong they will be reelected. This is due to the fact that people are scared of change. By reelecting a congressman they are well aware of what they will be receiving, but if they elect a new congressman the ball is in the air.
By doing this you can also limit the amount of corruption because people would not want to invest in a congressman who would only be in office for a limited amount of terms. If the limit is set to three terms congressmen would have to please the people to get reelected.