Blood has an official 'shelf life' of 6 weeks. The tendency to use old blood first to rotate stocks would mean that much of the blood used would be over the two week limit said to be dangerous.
Blood can't be frozen or the red blood cells burst. Huge volumes are used in transplant and heart surgery that have been much more common over the last few years. Much of the blood used in these cases ends up on the floor. If a blood bank supply reaches the two week limit, supplies are said to be critically low. There needs to be a redevelopment of the practice of blood supply and distribution, Perhaps with alternatives to whole blood and the types surgery being considered. 'Keyhole' heart surgery is one option that has that saves the need for huge transfusions, and patient stress.
Something I considerd as a comparison. How long can pasteurized, homogenized milk be kept in the fridge before it goes sour ?