The default point rule is set to one year, the point rule when changed will not apply to all customers, only new customers and restarted loyalty customers after their rank points expire.
To change the point rule click the Adjust Point Rule button at the top of the admin. A dropdown will appear from there you can change the existing point rule and click save your changes to complete the change. This change will apply to all ranks.
Point Rule is used to cycle out inactive customers from being in high ranks and keep customers earn again every point period. Even though points and rank reset, your customer and you are still able to see their lifetime points. Thus allowing you to reward or filter customers with high or low lifetime points.