I think the variance is a good idea, too. Since I could only find references from April 2010 that still states 6 hours, I emailed the FDA and this is what I heard... Hi, Have the regulations (Title 21, Volume 7) been updated since April 2010? I’m particularly wondering about section 606.122. Thanks, Becky Dear Ms. Snedeker, Thank you for your inquiry. The Center for Biologics Evaluation and Research (CBER) is one of seven centers within the Food and Drug Administration (FDA). CBER is responsible for the regulation of biologically-derived products, including blood intended for transfusion, blood components and derivatives, vaccines and allergenic extracts, human cells, tissues, and cellular and tissue-based products (HCT/Ps), gene therapy and xenotransplantation products. There were no changes to 21 CFR Part 600 for 2011. I hope this is helpful. Sincerely, Lonnie