386.3. For such Passive Abilities, they will be active until they have been applied to the specified number of events, after which point they will become inactive.
386.3.a. If such a Passive Ability says "you may" or "they may" as the first part of the ability after the "once each turn," the controller of the source of the Passive Ability chooses whether or not to apply the ability to the event in question. If they do not, the Passive Ability is Ignored during that event. See rule 764. Ignoring Effects for more information.