Expiring passwords

You can force a change of password, and warn about the upcoming change, by adding

:passwordtime=90d:\
:warnpassword=5d:\ 

to your login.conf file in /etc.

You may also be interested in this article: http://www.nas.nasa.gov/Groups/Security/epasswd/article.html and this section of the Handbook: http://www.freebsd.org/cgi/man.cgi?query=login.conf&sektion=5