  We consider the evolutionary state of the black-hole X-ray source GRO
J1655-40 in the context of its transient nature. Recent optical observations
show that the donor in GRO J1655-40 is an intermediate-mass star (~ 2.3 solar
masses) crossing the Hertzsprung gap. Usually in such systems the donor's
radius expansion drives a near-Eddington or super-Eddington mass transfer rate
which would sustain a persistently bright accretion disk. We show that GRO
J1655-40 is close to a narrow parameter range where disk instabilities can
occur. This range corresponds to a short-lived evolutionary stage where the
secondary's radius expansion stalls (or reverses), with a correspondingly lower
mass transfer rate. If GRO J1655-40 belongs to this class of transients the
predicted accretion rates imply large populations of luminous persistent and
transient sources, which are not seen in X-rays. The transient nature of the
related system GRS 1915+105 may reflect spectral variations in a bolometrically
persistent source rather than a genuine luminosity increase.
