2 resources from icann.org we point founders to, and the questions each answers.
📄 Article
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ICANN's own answer to whether you can own a domain forever: registrars sell registrations in one-year increments and the remaining term can never exceed ten years.
ICANN's guide to renewal: if you do not renew before the domain expires you risk losing it for a short time or for good, and ICANN cannot give it back.