I knew that the default is to provide membership safeguard by
retaining machine account passwords two deep, so the auth can
be with the prior if the password presented by the machine does
not match the current password. This provides for a little tolerance
for such as reimaging, etc..
What I did not know was that the account would be disabled if
two password changes were missed, and I have to question this.
One can disable, on a per-machine (or OU via GPO) basis whether
a machine will change its password at all. This means if there is
such a disabling, then the mechanism could not be blind to the
policy under which the machine that has not changed it password
operates, etc. - all becoming a little complex. Of course, if this
is so, that also means that if a machine is not booted for a couple
months then its membership is automatically defunct.