All of the NFTs you know and love today, have their data stored their on centralized servers (images, video, etc). What is only stored on the Blockchain is just the properties of the NFT itself. While you're basically the "owner" of the NFT, you could lose technically lose it if the centralized server hosting the content of the NFT goes down.
NFTs to me are just a temporary tokens used to serve a particular purpose frombthe intention of it creators, which makes it not a currency but a token, and investing on token must be with ultimate care because many are scam tokens in the market, as long as they are controlled under a central server developers they can be attacked and or controlled by anyone.
So, what's the point of investing in NFTs if they can disappear in an instant? Unless all of the content is stored on the Blockchain itself, I don't see how NFTs will be able to last forever. Are there already solutions in the works that I'm not aware of? Please enlighten me on this. Your input will be greatly appreciated. Thank you. 
You shouldn't invest on tokens ror a long time because they can cease to exist anytime especially during high volatility when bitcoin and crypto market goes bearish, some of these tokens goes down completely along.