They did on most of the flight systems, but I believe I read somewhere that even on their retirement date, many of the aircraft still had tubes in the avionics

They did on most of the flight systems, but I believe I read somewhere that even on their retirement date, many of the aircraft still had tubes in the avionics bays. A complete replacement programme was just too expensive, and what they had worked, so they stuck with it. Had Concorde been a profitable aircraft, then it might have been a different story...