  Inclusive heavy-flavour decays can be described through $1/m_Q$ expansions
derived from QCD with the help of an operator product expansion. I sketch their
methodology and apply them first to semileptonic B decays; $|V(cb)|$ can be
extracted from $\Gamma _{SL}(B)$ and $\bar B \to l \nu D^*$ with the result:
$|V(cb)|_{incl} = 0.0413 \pm 0.0016_{exp} \pm 0.002_{theor}$, $|V(cb)|_{excl} =
0.0377 \pm 0.0016_{exp} \pm 0.002_{theor}$. The lifetimes of charm and beauty
hadrons are discussed. The charm lifetimes are predicted/reproduced as well as
could be expected. Predictions on B meson lifetimes agree with available data;
$\Lambda _b$ baryons are predicted to be shorter lived than B_d mesons by no
more than ~ 10% - in marked contrast to present measurements. I evaluate the
situation and comment on recent theoretical criticism. The importance of the
concepts of global vs. local quark-hadron duality is pointed out.
