This module allows administrators to set an expiry date on passwords. Users that do not renew their passwords within the given time will have their passwords reset to a randomly generated one.
You can schedule warning messages notifying users when their password is close to expiry. If you have the actions module enabled, then you can also schedule emails to be sent. Both messages and emails can use (but do not require) the token module
and provides tokens such as [pass-expire-days-left] and [pass-expire-month].
Note: In order for password expiry to work properly, cron must be scheduled regularly.
Vote for this module at drupalmodules.com