set up password change regularly with certain rules

[Kent Paul Dolan]

Just remember, the harder you make a password to
remember, and the more often you make a user
memorize a new hard-to-remember password, the better
the chance you're going to find that password
written on a post-it note and stuck to the edge of
the monitor. With gobzillions of Internet sites
_also_ demanding passwords for access today, you're
fighting for mindshare in an ever more overloaded
resource, the fallible human brain.

xanthian.