  We study the short-time and medium-time behavior of the survival probability
of decaying states in the framework of the $N$-level Friedrichs model. The
degenerated and nearly degenerated systems are discussed in detail. We show
that in these systems decay can be considerably slowed down or even stopped by
appropriate choice of initial conditions. We analyze the behaviour of the
multilevel system within the so-called Zeno era. We examine and compare two
different definitions of the Zeno time. We demonstrate that the Zeno era can be
considerably enlarged by proper choice of the system parameters.
