This is the number of minutes, from 1 to 480, before a PSK update completes at which the system escalates to a critical alert about the pending key change. This later, more urgent threshold than the warning timer gives an admin a final chance to intervene, for example to abort a bad key push, before the new PSK actually takes effect and traffic could be disrupted. For example, with pskMapCriticalTimer at its default of 30 minutes, an unattended key rollover started overnight would raise a critical alert half an hour before cutover, still inside a typical on-call response window.