For long-term NFT investing, I would recommend you research where/how the art you purchase is hosted, since it will be completely out of your control & you may have to do some additional work to ensure the art "stays up" / is accessible after the seller grabs your cash & bolts.
Also worth noting, like any art-based investment, it's only worth what someone else is willing to pay for it. So try to remember what makes you think a given price something is worth now, because to get that value back + ROI, you will have to convince another schlub that it's worth _more_ than whatever price you are currently willing to pay.