  The problem of the final state interaction in quasi-elastic $(e,e')$
scattering at large $Q^2$, is investigated by exploiting the idea that the
ejected nucleon needs a finite amount of time to assume its asymptotic form. It
is shown that when the dependence of the scattering amplitude of the ejected
nucleon on its virtuality is taken into account, the final state interaction is
decreased. The developed approach is simpler to implement than the one based on
the color transparency description of the damping of the final state
interaction, and is essentially equivalent to the latter in the case of the
single rescattering term. The $(e,e')$ process on the deuteron is numerically
investigated and it is shown that, at $x=1$, appreciable finite formation time
effects at $Q^2$ of the order of 10 (GeV/c)$^2$ are expected.
