Root password lifetime default

Hello everyone!
Could someone tell me where and how can I change the default value for root password lifetime. Now it is 30 days and I want to increase it on 90.
The passwd -x doesn't help because after 90 days it will again go to default value. The OS is Tru64 5.1 and enhanced security is turned on.
Tnx in advance!

/tcb/files/auth should be the equivelant of /etc/shadow on some other variants of UNIX; you maybe have a man page for auth. I don't have that OS atm so don't know the format offhand.