What happens if you cancel the monthly plan after a few months

If you cancel an iCloud subscription, after 30 days your data will be purged to get your used storage back down below 5GB. It is a monthly subscription, a rental of online storage if you prefer to think of it that way. You only get access to the extra storage for as long as you continue to pay for it.

Hello Portlandbrit,

Thanks for using the Apple Support Communities. We understand that you have questions about your iCloud storage plan and what happens once you cancel it. It mentions in article, Downgrade or cancel your iCloud storage plan:

"If your iCloud storage exceeds your new storage plan capacity, iCloud won't sync or update your information. iCloud updates again when you increase your storage capacity or delete information to make more space."

As for buying storage plans, it doesn't appear there is an option to make this purchase as a one-time only charge and is only available as a monthly subscription. You can read more about this at, iCloud storage plans and pricing.

Best regards.