  We revisit the field effect procedure used to characterise the slow dynamics
of glassy Anderson insulators. It is shown that in the slowest systems the
procedure fails and the "characteristic" time values extracted are not
intrinsic but determined by the experimental procedure itself. In other cases
(like lightly doped indium oxide) qualitative indications about the dynamics
might be obtained, however the times extracted cannot be seen as characteristic
relaxation times of the system in any simple manner, and more complete
experiments are necessary. Implications regarding the effect of carrier
concentration on the emergence of glassiness are briefly outlined.
