No, GRE scores are only valid for 5 years. A weak grade in a political science or economics course can affect your competitiveness even if the overall GPA appears to be good. Every applicant is different with different backgrounds, interests, and plans for the future. The Admissions Office cannot make standard recommendations that would fit every applicant. Applicants should pursue their interests and make choices about internships, work abroad, and their education to meet their needs and interests.
Work experience is just one of many factors considered when evaluating an applicant.
The average age of the 2000 incoming class was 26. This work experience varies widely and is not necessarily directly limited to international relations. In addition to working in Washington, DC with the federal government, many incoming SAIS students have experience in the financial sector, consulting, in private industry, the Peace Corps, teaching abroad, as legal assistants. Those younger candidates have typically held directly relevant internships, away from campus, in international relations or politics during their summers. The average incoming class size for the Washington, D.C. campus is 130.