What is the isolation life of the standard digital isolator "DCL54x01"?

Toshiba Standard Digital Isolators have a structure that uses oxide film in the chip to insulate them. Therefore, the isolation life of the standard digital isolator can be predicted by applying the same concept as MOSFET gate-oxide breakdown over time (TDDB : Time Dependent Dielectric Breakdown ^{[Note 1]}).
"Magnetic and capacitive coupler for basic and reinforced insulation" ^{[Note 2]} has been standardized by the International Safety Standards under standard number IEC 60747-17: 2020 Ed. 1 and VDE V 0884-11, and the aforementioned TDDB test conditions have been defined.

The DCL54x01 series complies with VDE V 0884-11 standards by applying for reinforced isolation to the maximum operating isolation voltage V_IORM=1.0kVrms ^{[Note 3].} TDDB test is conducted at 1.2kVrms, a factor of safety (1.2) multiplied by the above V_IORM required for reinforced isolation. Also, the life determination point is 37.5 years ^{[Note 4]} @ 1.2kVrms on the extrapolation line of 1ppm defect rate required for reinforced isolation.
As a reference, in addition to testing the rated life required at a minimum for the above VDE qualification, we predict an isolation life of 70 years or more, exceeding the VDE specifications, under accelerated conditions of the test voltage.