Retired from gigs with the U.S. Navy, Veterans Administration (as it was then called), and mostly the National Institutes of Health, for a total of 40 years, in 2011. I had time off for grad school and a job as a audio-visual script writer and some contract writing editing work. I still do some writing for publication, of various kinds. I highly recommend retiring if/when you can do it. Just don't become sedentary -- keep going and doing. If you need to work to do so, do that.