Domain names and their registrations are regulated by an independent non-profit organization called ICANN (or in full, The Internet Corporation for Assigned Names and Numbers.)
ICANN has declared that you cannot buy a domain name permanently, and that has been the policy since the beginning of the internet. Who has been able to buy a domain name permanently? No one! Not even Bill Gates of Microsoft.com, or Elon Musk of Tesla.com.
Domain name registration is billed annually, but you can choose to pre-pay for up to a maximum of 10 years which guarantees that you will own the domain name for 10 years. You can always renew after each billing cycle elapses.