I haven't done it yet, but if you cancel your and contact them, I've heard you can get a refund for the months you haven't used. Even if you cancel but don't contact, you still can use the service until the end of your subscription.
My biggest thing stopping me rn is moving my emails away from proton mail and simpleogin (switched to mailbox.org and anonaddy free) and trying to convince myself I don't need port forwarding 😭