  In a recent Letter [Phys. Rev. Lett. 79, 889 (1997) and cond-mat/9702054] we
have demonstrated that the avalanches in the Bak-Sneppen model display aging
behavior similar to glassy systems. Numerical results for temporal correlations
show a broad distribution with two distinct regimes separated by a time scale
which is related to the age of the avalanche. This dynamical breaking of
time-translational invariance results in a new critical exponent, $r$. Here we
present results for $r$ from extensive numerical simulations of self-organized
critical models in $d=1$ and 2. We find $r_{d=1}=0.45\pm 0.05$ and
$r_{d=2}=0.23\pm 0.05$ for the Bak-Sneppen model, and our results suggest
$r=1/4$ for the analytically tractable multi-trade model in both dimensions.
