We investigate the entire evolution of the Dicke model, which is a two-degree-of-freedom interacting spin-boson model of great experimental interest. Our objects of study are the quantum and classical survival probabilities of initial coherent states and the corresponding classical evolution of the Wigner distribution in phase space. We show that major aspects of the system are uncovered by analyzing its long-time dynamics, such as whether the initial state is in a regular or chaotic region, in the vicinity of a separatrix, or yet close to an unstable periodic orbit. We demonstrate that a ratio of two between the quantum and classical asymptotic values of the survival probability is a clear indicator of maximal quantum ergodicity. In this case, the quantum survival probability develops a correlation hole, that is nonexistent in its classical version and results in a longer equilibration time for the quantum dynamics. These findings are corroborated by our analytical expressions for the survival probability and the equilibration time.