Recurrence time for a 1.4   M_⊙ neutron star accretor with a residual equatorial magnetic field of 10^8.5 G (solid) and for a 10   M_⊙ black hole accretor (dashed) with a helium disk described by Dunkel et al. (2006), for two values of the viscosity parameter α, of which 0.02 probably best describes the disk viscosity in quiescence. Disk instability becomes relevant to the right of the vertical line at 28 min. The circles indicate an age of 10 Gyr. The discontinuity in the slopes of the neutron star curves at an orbital period of 29 min is because the speed-of-light cylinder defines the inner disk radius beyond this period (Fig. 11).