If you only want the addon to stay attached to the subscription for a fixed number of billing cycles, you can set the addon billing cycle parameter for the addon while creating or updating a subscription.
Set up a recurring addon.
To add the addon to a new subscription, navigate to Subscriptions and click on Create New Subscription. Click Add Recurring Addon. Here you choose the addon and mention the billing cycle as well.
The addon will be added to the invoice for the new subscription. As the term progresses and more invoices are generated for each billing cycle, the billing cycle will decrement to become zero and the addon will be removed after.
To add the addon to an existing subscription, locate the subscription and click Edit Subscription.
Then click on the edit icon for an addon to change the number of billing cycles.
For the existing subscriptions, when an addon is added, a prorated invoice is generated based on the subscription term. The prorated period will be considered as one billing cycle as far as the add-on is concerned. If you add a billing cycle to an existing addon linked to a subscription, no charge will be raised. However, the billing cycles for the addon against the subscription will be increased by 1.
If there is a change of term for the subscription (for example, you change the subscription from monthly to quarterly) and the change is done via API, ensure that the billing cycle of the addon is passed as well. If not, the billing cycle of the addon will be reset to ‘forever', i.e., the customer will be charged for the addon indefinitely.