We investigate the large time behavior of solutions to nonlinear dissipative
wave equations of the general form
\[
\varepsilon u_{tt}+u_{t}-\Delta u=F\left(x,t,u,D_{x}u,D_{x}^{2}u\right);
\]
in particular, we study the dependence of the solutions $u=u^{\varepsilon}$
and of their life span $T_{\varepsilon}$ on the (small'' parameter
$\varepsilon$. We are interested in the behavior of $u^{\varepsilon}$
and $T_{\varepsilon}$ as $\varepsilon\rightarrow0$, and in their
relations with the solution v, and its life span T$_{p}$ , of the
corresponding limit equation when $\varepsilon=0$, which is of parabolic
type. We look for conditions under which either $T_{\varepsilon}=+\infty,\: or\: T_{\varepsilon}\rightarrow T_{p}\leq+\infty$
as $\varepsilon=0$.
