The RBC lifetime is about 120 days

The life cycle of a Red Blood Cell.

a) Kidneys respond to a lower than normal oxygen concentration in the blood by releasing the hormone erythropoietin. 
b) Erythropoietin travels to the red bone marrow and stimulates an increase in the production of red blood cells (RBCs). 
c) The red bone marrow manufactures RBCs from stem cells that live inside the marrow. 
d) RBCs squeeze through blood vessel membranes to enter the circulation. 
e) The heart and lungs work to supply continuous movement and oxygenation of RBCs. 
f) Damaged or old RBCs are destroyed primarily by the spleen.