The "expires" attribute in /etc/security/user is for specifying a particular date and time for a user's account to expire. If set, the account will be locked (not just password expired) after such date and time.
You can script what you want, though.
lsuser -a maxage ALL
will give you the maximum password in weeks for each user.
lssec -f /etc/security/passwd -s <username> -a lastupdate
will give you the time, in seconds since the epoch, for <username>.
I'm short on time right now, but can write something up in perl later, if you need it.
Rod Knowlton
IBM Certified Advanced Technical Expert pSeries and AIX 5L
CompTIA Linux+
CompTIA Security+