It makes them more independent. If they had a limitless amount of terms, they could just vote for whatever was suitable at that time and keep their political power. Since they won't be able to stay in the congress longer, then they can vote whatever they want because there's nothing that will affect whether or not they get elected again.
About 100 miles got my answer from answer.com
Answer:
The Crédit Mobilier scandal of 1872-1873 damaged the careers of several Gilded Age politicians. Major stockholders in the Union Pacific Railroad formed a company, the Crédit Mobilier of America, and gave it contracts to build the railroad. They sold or gave shares in this construction to influential congressmen.
They both had
priests
officials
traders
craftsmen
farmers
slaves
laborers
warriors
Yes, because it was one of the biggest elections ever