Effective temperature vs. cooling age for non-flashing sequences with maximum (red) and minimum (blue) initial M_H from a CE phase. Insets show the fraction of WD luminosity from H burning. Solid black lines represent SRLOF cooling tracks (Althaus et al. 2013), where short-lived H flashes occur. Thin violet lines indicate intermediate M_H values. Ages are measured from the start of the cooling branch. Horizontal dotted lines mark the T_eff range of the observed He WDs reported in Table 2.