I just want to add to this. If you are on sufficient release you could use secuirty policy to force this value to be low for subset of users. So you could kindly ask users to change their passwords.Then select users who did not change their passwords in given period and assign them policy with low expiration time. So when they log on they will be forced to change password. After this exercise you would remove this special policy from these users to get back to standard defaults.
If this is about new password policy then follow Julius' advice and use standard parameter for this.
Cheers