One could say that the meaning of the word Dhamma is related to the word Concept. The concept of "Nibbana" would therefore exist until all temporary realities cease, then what was conceptualized will be known as it is and knowknown to not have the characteristics suffering, being discerned as ultimate peace and happiness. The thinking about it and the Idea has characteristic of suffering because it only temporarily gains footing in the system in which all is happening. The concept is not the real thing if u know what i mean. So nibbana as a concept is in that sense a formed idea therefore will change, gaining temporary existence in a system. Nibbana as a reality is a possible state of the system, a state in which existence and matter gain no footing, this is brought about by tweaking the states of energy and information existing within the system.