For those following this thread, part of the reason we are changing our practice is this requirement from JCAHO to QC each open vial, this is the 2004 edition, I don't 2005 handy, but I don't think it's changed:
Standard QC.5.220The laboratory tests for reactivity the potency and reliability of reagents used for ABO grouping, Rh typing, antibody detection, and compatibility determinations on each day of use and when a new lot of reagents is first used.
Elements of Performance for QC.5.220
Each opened vial of antisera, reactive cells, and reagents is tested for reactivity on each day of use and when a new lot of reagents is first used.The laboratory confirms that each reagent reacts as expected. Results are documented.