Even with a TLD, going out of business is a concern. Take Freenom as an example, they had rampant abuse and ran into funding issues. People who previously used

Even with a TLD, going out of business is a concern. Take Freenom as an example, they had rampant abuse and ran into funding issues. People who previously used that service for free internal domains have been looking for a new home. What's different is that the public suffixes I operate cannot publicly host content, which should protect the service from the abuse concerns that plagued Freenom and other free public suffixes. That reduces cost and should keep the site running. I recommend buying your own domain if you don't mind the cost. A free solution for domains with TLS on internal networks is valuable to many.