The Connect Enterprise Manager can control for how long a password is valid. This is a security feature, called a Password Policy, that forces Connect users to reset their passwords after a period of time.
Password Policies can be configured in the Connect Enterprise Manager by going to Administration > Users and Groups > Edit Login and Password Policies. Here you will see the control called Passwords Expire After. If this is left blank, Connect user passwords will never expire. If it is set to a number, passwords will expire after that number of days.
To access this page you must login to Enterprise Manager as an Administrator.