The (minimal) frequency at which a model has to be re-validated. This is often determined in the model validation policy of the bank.
Note that the model validation frequency typically depends on the amount of model risk that is associated with the model. As an example, a model that is used extensively might have to be validated yearly while a model that is only used sparsely might have to be revalidated only once every three years. Typically, the amount of model risk that is carried by the model is expressed in terms of model risk tiers.