Some customers may purchase from you once, then never again. Customers like this will count toward your total active member count if they maintain a point balance. You can have Glow automatically set points to zero after a given timeframe if customers have been inactice (this means they have no earned or redeemed points in the timeframe you've selected).
To setup your points expiry, login to your account and go to "Settings > Account Settings > Advanced Settings > Behavior > Point Expiration".
Here you can select whether you'd like points to never expire (default) or select a timeframe.
Once you've made your selection, click "Save Settings". When the point expiry is triggered, you will see the points deducted from the member's account and the deduction type will be "Manual".