On the nilpotency index of the radical of a module category

Let $A$ be a finite dimensional representation-finite algebra over an algebraically closed field. The aim of this work is to determine which vertices of $Q_A$ are suficient to be consider in order to compute the nilpotency index of the radical of the module category of $A$. In many cases, we give a formula to compute such index taking into account the ordinary quiver of the given algebra.