NFTs can live ‘forever’ because they exist in a decentralized blockchain but the artworks they point to might cease to exist. For people purchasing as an investment, it’s important that the high resolution file stays around forever.
As an example, there’s no point me putting the file on my server, I die, my server hosting gets stopped and the file disappears. Surprisingly, this is the case for some NFTs that have sold for millions of dollars.
All my NFT high resolution files are hosted on what’s called decentralized storage that, as long as there’s no global catastrophe, has a great chance of being there forever.
For example, you can access a file using https://ipfs.io/ipfs/ followed by the CID:
(If this is slow or doesn’t work, try one of the other gateways linked above)
This provides a low resolution file of my Purple Iris that I have uploaded just for this example and will be there ‘forever’.