Multi-objective Evolutionary Algorithms evolve a population of solutions through successive generations towards the Pareto-optimal Front. One of the most critical questions faced by the researchers and practitioners in this domain, relates to the number of generations that may be sufficient for an algorithm to offer a good approximation of the Pareto-optimal Front, for a given problem. Ironically, till date this question largely remains unanswered and the number of generations are arbitrarily fixed a priori, with potentially punitive implications. If the a priori fixed generations are insufficient, then the algorithm reports suboptimal solutions. In contrast, if the a priori fixed generations are far-too-many, it implies waste of computational resources. This paper proposes a novel entropy based dissimilarity measure that helps identify on-the-fly the number of generations beyond which an algorithm stabilizes, implying that either a good approximation has been obtained, or that it can not be obtained due to the stagnation of the algorithm in the search space. Given that, in either case no further improvement in the approximation can be obtained, despite additional computational expense, the proposed dissimilarity measure provides a termination criterion and facilitates a termination detection algorithm. The generality, on-the-fly implementation, low computational complexity, and the demonstrated efficacy of the proposed termination detection algorithm, on a wide range of multi-and many-objective test problems, define the novel contribution of this paper.