What have we still to learn about the Inverse Power Model?

Much about insulation aging has been understood, thus leading to complex physical life models. However, for design and testing purposes of power insulation, more pragmatic phenomenological models are often used, first of all the so-called 'Inverse Power Model', also referred to as 'V-t characteristic'. Yet, the Inverse Power Model is sometimes misused and misinterpreted, not only in technical-scientific papers, but also in International Standards. The purpose of this paper is acquiring a deeper understanding of this seemingly-trivial model, so as to foster a better and more insightful use of the Inverse Power Model both for design and for testing purposes.