http://protonmailrmez3lotccipshtkleegetolb73fuirgj7r4o4vfu7ozyd.onion/support/inactive-accounts
What happens when you’re inactive If you have a Proton Account on a Free plan that has been inactive for one year (12 consecutive months) or more , your account and all data associated with it (including but not limited to emails, contacts, calendars, and files stored in the cloud) may be deleted.