I didn't do it, but my old next door neighbor has done non-stop CONUS to IRAQ to CONUS in the B52... he made the return trip several thousand pounds lighter than when he left and had to refuel several times enroute.
16.5 hours in a B52 with the helmet on the whole time. Not as long as CONUS to Iraq and back but the only war going on when I fly BUFFS was the Cold War.