Debates abound on what is the proper period or time frame between password changes.
In reality, the best time frame between password changes is every time they are used. This is in the belief that reusing a password used a year or more ago is a security risk. Fore example, if a required change period is 90 days and the system will not allow you to reuse a password for 5 change periods, you will not be able to reuse a password for over a year and a half. Systems blocking reuse for 10 change periods result in prohibiting reuse for over 3 years. Somehow, there is a security risk I a user uses the same password in 899 days.