Only what you sell.

If you let customers change their subscription interval, they can now only choose from the frequencies your products are actually sold on.

Before, "Deliver every" was a free number field and a Day, Week, Month or Year select, so a subscriber could enter a frequency you never sold, such as every 3 or 100 years. Now, in both the customer portal and the Shopify customer account's Edit order window:

• "Deliver every" is a single list of the frequencies the products are sold on.
• A frequency the subscriber is already on that you do not sell stays visible as "(current)".
• When there is only one frequency, it is stated in a sentence instead of a list.
• The list follows product changes the subscriber has made but not yet saved.
• A save with a frequency outside your plans is refused, and the customer account shows the stated reason.

This is on by default. If you want subscribers to keep entering any frequency, open Customer permissions, tick "Customer can Change subscription interval", and choose "Any frequency" instead of "Only the frequencies the product's subscription plan offers".