The
absorption and ejection of gravitons by blackholes, indeed by every
object
in the
Universe, is frequent and often continuous. It cannot help but
be so. Every
object in the Universe, from the least substantial of blackholes to the
mightiest of supergalactic clusters, is within the
gravitysheath interface of a larger object - with the
largest gravitysheath interface of all being that of the Universe
itself. Most
objects have a
gravitonosphere
and thus smaller objects are often not just
inside
the gravitysheath interface of a larger object but within
its gravitonosphere as well. Thus it is that the constant interchange
of gravitons out of one gravitysheath interface into another is the
commerce
of the Universe.
Note that the mass of a blackhole, as described here, is the
absolute mass and not the
gravitational mass.