Password Policy: Minimum Password Age

In Windows Vista, the Minimum Password Age setting determines the period of time in days that a password can be used before the user must change it. You can set a password to expire anywhere between 1 and 999 days, or you can allow changes immediately by setting the minimum password age setting number of days to 0.

Minimum and Maximum Password Age

The Minimum Password Age setting must be lower than the Maximum Password Age setting unless the Maximum Password Age is set to zero, in which case the password never expires. If the Maximum password age is set to zero, the Minimum password age can be set to any value between 0 and 998.

Password Best Practices

Best practices suggest setting a Maximum password age of 60 days. This way, there is a small window during which the password might be hacked and used. 

Setting a Minimum password age is useful in conjunction with Enforce Password History to prevent users from entering new passwords repeatedly to bypass Enforce Password History.