How long is banked blood cells going to last after you get the transfusion?

Less than a month. : It depends on the age of the transfused blood. The normal life span of a red blood cell is about 30 days before it is destroyed in the spleen. Transfused blood is usually not as hearty as natural blood so i would expect it to degrade less than 30 days.

Average 3 months.: "most relevant studies show that approximately 20% of the rbcs are lost in the first 24 hr after transfusion. The average life span is 94 days after a storage period of 42-49 days." this can be much shorter depending on the underlying medical condition that may cause ongoing hemolysis. Ref: cell mol biol (noisy-le-grand). 2004 mar;50(2):197-203. Survival of the fittest?