The generalized Allen-Cahn equation,with nonlinear diffusion, D = D(u), and potential, F = F (u), of the formandrespectively, is studied. These choices correspond to a reaction function that can be derived from a double well potential, and to a generalized degenerate diffusivity coefficient depending on the density u that vanishes at one or at the two wells, u = ±1. It is shown that interface layer solutions that are equal to ±1 except at a finite number of thin transitions of width ε persist for an either exponentially or algebraically long time, depending upon the interplay between the exponents n and m. For that purpose, energy bounds for a renormalized effective energy potential of Ginzburg-Landau type are derived.