On the other hand, the A6 aircraft, designed in 1957, and it's electronic jamming version, the EA6, have been contracted for a "re-wing" and "re-engine" yet again. I have no idea (without looking it up) what the current "dash variant" of these planes are today. Similarly, the B52 (1950-51 design) is also still in service.
Many years ago, the master models and engineering drawings for the A6/EA6 wings were destroyed when a warehouse collapsed on Long Island. I was a member of the team that reconstructed their geometry by running around and measuring airplanes. I went through the original engineering notebooks from 1957. I even got to meet LeRoy Grumman (though I had mistaken him for Leon Grumman and repeated that canard for many years) and go through his recollections of the program. It was quite an experience.