Maintenance
The persistence of a learned behaviour over time after active teaching has ended.
Maintenance is whether a skill sticks. A learner can perform a behaviour perfectly during teaching and lose it entirely within two weeks if the conditions that support it are removed.
Fluency is the best predictor of maintenance. Skills learned to a high rate with low variability are far more durable than skills learned to a fixed accuracy criterion. A learner who can read at 200 words per minute will maintain that skill through disruptions that would erode performance in someone who reads haltingly at 60.
Maintenance probes - brief, unannounced checks on skills that are no longer being actively taught - are the only way to know whether maintenance is actually happening. Without them, you're assuming. Skills assumed to be maintained are often quietly gone.