Account time expiration question

Dear managers,

We're currently using the "enhanced security" option on a system running
tru64 v5.1B.  Some of the UNIX accounts were setup for user access and
NO users were accessing the accounts.  After a while we noticed that
these accounts got expired.  

We have a user "template" so the password doesn't expire but, this
didn't prevent the fact that the accounts itself were expiring since no
one logs into the accounts.  We want to keep some accounts without time
expiration and some others that do expire (like it is now).  

Regards,

Orlando G.