Q. I served 9.5 years in the Air Force and just short of five years for the FAA under CSRS. When I left the FAA in late 1987, because of a misunderstanding of how CSRS worked, I thought I had to withdraw my contributions to CSRS because I had fewer than five years. Counting most of my Air Force time, I have 39 years of substantial contributions to Social Security. I returned to government employment two years ago and am considered CSRS Offset. Since I plan to retire in four years, I am trying to determine my best option regarding…