  Properties of unstable false vacuum states are analyzed from the point of
view of the quantum theory of unstable states. Some of false vacuum states
survive up to times when their survival probability has a non-exponential form.
At times much latter than the transition time, when contributions to the
survival probability of its exponential and non-exponential parts are
comparable, the survival probability as a function of time t has an inverse
power-like form. We show that at this time region the instantaneous energy of
the false vacuum states tends to the energy of the true vacuum state as
$1/t^{2}$ for $t \to \infty$.
