Q: I was in the Air Force from May 1980 to June 1993. I took a separation incentive. I have been in Federal Employees Retirement System from 1993 to present. What do I do to get the best possible retirement pay? Buy back time? Would I have to pay back the separation incentive? I am 48 years old. A: If you want to get credit for your years of active duty service, you’ll have to make a deposit to the civilian retirement fund. In your case, that would be 3 percent of your basic military pay, not including any allowances…