IATF 16949: 2016 standard 220.127.116.11 e) says "periodically test the contingency plans for efficiency (eg simulations as appropriate)".
Also in article c) "prepare contingency plans for continuity of supply in the event of any of the following: key equipment failures (also see Section 18.104.22.168.1); interruption from externally provided products, processes, and services; recurring natural disasters; wastage; utility interruptions; labor shortages; or infrastructure disruptions".
In the following case, for the cases specified in article c); testing or simulation is mandatory. The organization can determine the frequency of testing or simulation according to the risk and its impact on the customer.
So, at least for all cases, you can test or simulate once; then you can determine the frequency according to the results, risk.