samba - Jun 2007 - Do Machine Accounts Expire?

I recently started playing with pdbedit to set the maximum password age policy
on v3.0.25a.  After setting
this policy, I see that running pdbedit -Lv shows the machine accounts expiring
in the same time frame as
the user accounts.  So my question is do the machine accounts actually expire
just like user accounts?  If
they do, is there any way to set the machine accounts not to expire as a group
instead of setting them not
to expire one at a time?

Thank you in advance.