Being in the Old Guard

Article 1 Section 2 of the Constitution stipulates the age limit to join the House of Representative as 25. Article 1 Section 3 of the Constitution stipulates the age limit to join the Senate as 30. Why isn't there a stipulation that requires those in the House and Senate to retire at a certain age? What might that age be? If we are not going to impose term limits maybe there should be age limits on both ends, entering and exiting. I'm getting really tired of the same staid faces which usually represent the same staid ideas.