  The computed $\log(\tau/{\rm y})$-$\log(m/m_\odot)$ relation for the stellar
initial mass range, 0.6-120.0, and the stellar initial metallicity range,
0.0004-0.0500, tabulated in an earlier attempt (Portinari et al. 1998) is
fitted to a good extent by a four-parameter curve, expressed by a double
power-law, for assigned stellar initial metallicity, which can be reduced to a
three-parameter curve, expressed by a single power-law, for the whole set of
stellar initial metallicities. The relative errors do not exceed about 2% and
4%, respectively. The extent to which the interpolation curve, expressed by a
single power-law, can be extrapolated towards both high-mass and low-mass
stars, is also investigated. High-mass star lifetimes are understimated by a
factor less than 2 up to $m/m_\odot= 1000$ and by a fiducial factor less than 4
up to infinite. Low-mass star lifetimes are overstimated by a factor of about 3
down to $m/m_\odot=0.25$ and by an unacceptably large factor down to
$m/m_\odot=0.08$. As a simple application, the star mass fraction of a single
star generation with stellar initial mass function defined by a power-law, is
plotted vs. the logarithmic stellar lifetime. The star mass fraction declines
in time at a decreasing rate for mild stellar initial mass function and at an
increasing rate for steep stellar initial mass function, where a linear trend
is exhibited for a value of the exponent close to the Salpeter's value, equal
to -2.35.
