User resetting password, week later needing to reset it again
Here are some suggestions/things to check based on your description:


If the user passwords on production are reverting after a recent deployment, check to make sure that your settings.php file on production doesn't point to the development instance's database (you may be inadvertently repointed production to a backup copy/development copy of the database by pushing changes in settings.php).
Check to see if your site is utilizing a password management module.  If so, doublecheck/resave expiration settings (as well as if any security/recommended updates are available). Common password management/expiration modules include:


Password Policy
Force Password Change

Check to see if there are any custom rules (either using Rules module or programmatically implemented with a custom module) in place that force a user to reset password after a set duration/period of time/number of logins.
Check to see if the site's user accounts are tied to an external user account provisioning/login system such as LDAP or a Single Sign On service (as well as if any security/recommended updates are available). If one of these are in place, then you may need to check password expiration policies at the account provider. Examples SSO service modules for Drupal include:


Janrain - integration with the commercial Janrain service
Google Apps Authentication
SimpleSAMLphp Auth - integration with the open source library SimpleSAMLphp
HybridAuth Social Login - integration with the HybridAuth library
Bakery - SSO among Drupal installations on the same parent domain
Account Sync - provides SSO functionality and account info synchronization among Drupal installations.