By what criteria were the 'good-until-revoked' licenses regarded?

The 'good-until-revoked' licenses are characterized by the fact that they remain valid until formally revoked by the licensing authority, rather than having a predetermined expiration date. This means that a driver can continue to operate under this license as long as they comply with the law and maintain eligibility. Essentially, there is no time limit imposed on the license's validity unless an issue arises that necessitates revocation, such as legal infractions or failure to comply with driving laws.

In contrast, licenses that have a specific expiry date usually require renewal after that date; thus, those are clearly not 'good-until-revoked.' Similarly, licenses requiring annual renewals indicate a fixed period of validity, which again does not align with the concept of being valid until revoked. The option mentioning frequent testing does not apply to the 'good-until-revoked' criteria, as this type of license does not stipulate regular testing requirements for its continued validity.