  We present some straightforward applications of the QCD heavy quark
expansion, stated in previous papers [1-3], to the inclusive widths of heavy
flavour hadrons. We address the question of the $D_s$ lifetime and argue that
-- barring Weak Annihilation (WA) -- $\tau (D_s)$ is expected to exceed $\tau
(D^0)$ by several percent; on the other hand WA could provide a difference of
up to $10\div20\%$ of {\it any} sign. We extract $m_c$, $m_b$ and $|V_{cb}|$
from $\Gamma\ind{SL}(D^+)$ and $\Gamma\ind{SL}(B)$. The values of the quark
masses are somewhat higher, but compatible with estimates from QCD sum rules;
we obtain $|V_{cb}|\simeq 0.043$ for $\tau (B)=1.4$ psec and
$BR_{SL}(B)=10.5$\% . We discuss the associated uncertainties in the $1/m_Q$
expansion as well as some consequences for other electroweak decays.
