An NFT is worth the ownership stake of the server that it points at. This is a huge problem. Jacob Kastrenakes writing for the Verge details the problems, the solutions, and the problems with those solutions. Basically, as long as an NFT is corrected backed off a distributed server infrastructure, and the people running that infrastructure do a good job, and someone keeps paying for all of this, your link will keep pointing to your asset. That is really what an NFT is: a promise that someone will maintain the infrastructure for you to keep accessing your file on a distributed network.