Subscription length
The length of a subscription is controlled by the Stop renewing after field. This allows you to end a subscription after a predetermined amount of time. Subscriptions for subscription products with a value in this field have a maximum length, after which they no longer renew and are no longer active.
Subscriptions for subscription products with Do not stop until cancelled set in the Stop renewing after field can renew indefinitely as long as renewal payments are successful.
For example, consider a one year magazine subscription, billed monthly, with a fee of $5/month. The length of the subscription would be 12 months and the billing period would be one month. In the subscription product details, this would be:
Subscription price: $5 every month
Stop renewing after: 12 months
Subscription length and billing period are not the same thing. The subscription length is the length of the entire subscription from when it starts to when it stops renewing, not a single billing period within that subscription.