Oubliette,
The shelf life of all the components in blood vary by years, so they are seperated and stored appropriatly at different temperatures. Then we give what is needed, blood loss or low Haemaglobin. give red blood cells.
Jw's have really confused what 'blood' and 'fractions' are to its members. Blood is the combination of all these factors whereas most JW's think of blood as a 1L bag of red stuff. It isn't, it's red blood cells, a small fraction of blood.