“Rule 07” was proposed 2 years ago as a convenient rule of thumb to estimate the dark current density for state-of-the-art planar, ion-implanted, p / n HgCdTe photodiodes fabricated in layers grown by molecular-beam epitaxy (MBE). The best reported HgCdTe devices from other laboratories had dark currents no lower than the rule and often higher. In the intervening time we have continued to compare the rule with performance obtained by ourselves and others to see if it stands the test of time. We also examined why it succeeds in approximating the dark current density over the thermal infrared wavebands (>4.6  μ m cutoff). It turns out that the rule has held up well, still predicting dark current density values within 0.4× to 2.5× over about 13 orders of magnitude. At least at mid-wavelength infrared–long-wavelength infrared wavelengths, where the dependence is exponential with inverse cutoff and temperature, the behavior can be explained by Auger 1 processes and the diode architecture. This has significant implications for high-operating-temperature devices.