Most of the companies offering the service say that the stem cells from the blood can be used from 10 to 15+ years after collection (and perhaps longer, although they probably don't have enough data to make 100% certain claims at this point).
So are they separating the stem cells from the blood and storing them, or storing the blood itself? I guess I need to talk to my wife who works blood bank at a local hospital, but I have the impression that donated blood is discarded within months if not used.