Owning a domain name forever can be tricky. For instance, most of the domains for sale are selling just the name, even though the website has to be hosted on a web-hosting platform. This means that the vast majority of domains last as long as the domain name registrar that they are hosted on. These companies manage the reservation of internet domain names and host them on their platforms. Some of the most-known examples are GoDaddy.com and Domain.com.
So, in theory, to own a domain name forever, you would need to buy both the domain and the web-hosting services that will serve as a home for that domain as long as you are able or willing to keep it running. And who knows, perhaps one day you end up owning not only one of the most expensive domain names in the world but also a highly valuable hosting platform that can keep making you money even after the sale of a domain.