I cannot conceive of such a situation, because the necessity standard would always apply. Anyone, including a member of the media, can bring an application to review this order. Any judge ruling on the extension or prolongation of such an order would have to assess whether it continues to be necessary. They would have to hear evidence, say after six months or a year, that the investigation is ongoing or has concluded or whatever, and make their assessment. Contextually, it's my view that the scenario where it would go on forever and be forgotten is impossible.
On November 7th, 2018. See this statement in context.