As I wrote in another comment, US Tech Force participants doing 2-year stints won't qualify for the gov't backed retirement (unless they were prior military, prior civil service, or find a non-term appointment to follow this stint with). You need three years to keep the 5% TSP (401k equivalent) match, which is similar to many private companies. You also need 5 years to qualify for FERS (if you quit before then you can get your contributions back, but that's optional as you may want to come back to gov't later and have the years count).