  The lifetime differences of bottom hadrons are known to be properly explained
within the framework of heavy quark effective field theory(HQEFT) of QCD via
the inverse expansion of the dressed heavy quark mass. In general, the spectrum
around the endpoint region is not well behaved due to the invalidity of $1/m_Q$
expansion near the endpoint. The curve fitting method is adopted to treat the
endpoint behavior. It turns out that the endpoint effects are truly small and
the explanation on the lifetime differences in the HQEFT of QCD is then well
justified. The inclusion of the endpoint effects makes the prediction on the
lifetime differences and the extraction on the CKM matrix element $|V_{cb}|$
more reliable.
