there are 100 percent legitimate concerns about having retired commissioned officers serve as SECDEF. however im not sure practically how much of a difference four years versus seven years in retirement makes in their civilian character. any retired commissioned officer is likely going to retain at least some of their mindset from time in the military. especially somebody with stars. i think those concerns will be present whether they are retired for four years, seven years, twenty years, whatever. IMO the seven year rule is more about preventing the appearance of a conflict of interest.