We also have the same issues. We keep the cells in the refrigerator when not in use. I also split my monthly shipment receiving 2 vials in one shipment and then 1 vial in a second shipment 2 weeks later, trying to have fresher reagent in use. Quotient is working on a C3 check cell prep kit that will allow you to make your own in house, which should be much stronger since the 28 day expiration will start there instead of at the manufacturing facility. Looking foward to whenever that is ready for release.