This read-only Integer32, ranging 5000 to 75000 milliseconds, sets how long each unit will wait before declaring the peer unit dead specifically due to an interface check failure, as opposed to the general unit holdtime in cufwFOUnitHoldtime. An admin tunes this separately from the unit-level holdtime because interface-level failures may warrant a different tolerance for transient issues. A shorter value here relative to the unit holdtime would mean interface-based failure detection triggers a failover faster than a general peer-silence timeout would.