Because the retention period changed and the engineering did not.
The Component That Sets Service Life
A sealed vacuum does not stay perfect. Annulus materials outgas over years and hydrogen and helium migrate through steel, which is a property of the metal rather than a defect. The getter absorbs it, and its capacity is finite. On saturation, performance declines with no alarm and nothing visibly broken.
The Arithmetic That Follows
Under the current 55 year retention limit confirmed by the Human Fertilisation and Embryology Authority, no vessel lasts the life of the samples in it. Across a single patient’s storage, the laboratory will move those samples between vessels more than once.
What That Changes
Transfer becomes a planned, repeated, documented operation rather than an exceptional one, and every transfer is a warming exposure. Write it up as a defined procedure with timing discipline and an audit trail rather than an ad hoc job done on replacement day. When specifying, ask what a warranty covers on the vacuum specifically, since that determines when the next transfer happens. Larger vessels such as the CryoBank Series are the usual destination.
