It is true that members of Congress have no term limits. Members of the House of Representatives are elected to two year terms. They can run for reelection every two years and there is no limit on the amount of times you can run for reelection. In the Senate, Senators are elected to six year terms and can run for reelection as many times as they want. These rights are granted in the Constitution of the United States of America.
The original purpose of the Selective Service Act of 1917 was to draft Americans into the armed forces. This was used as a means to increase the size of the American army during World War I.