Its impossible to have one or two coins in crypto space because one or two coins can't solve all the problems we have in this world in every aspect of technology or others, if you want to keep a coin for a long time make sure the coin or token solves one or two problems in crypto space or the world, this type of coins don't die easily because they have real use cases, its simple as that
Coins that are suitable for long-term investment are those that already have a product. By owning a product, a coin or token will continue to be traded in the market, especially if the project is able to make a profit, I think investors will continue to hunt for the token or coin and expect profits from the company.
Seen projects launched their product but token now is dead. Unfortunately there is no guarantee that a coin that solves problem will not really die, its all up to the community supporting the project. For users to support it means it really will have a good impact to them not just because of the price though its one of the factor. I wouldn't use ETH if it drops so much that disappoints me anymore. I would rather be going into ADA that way i'm way getting them for a very low price. What problems does your coin solve may not really be for a long term which is why devs discuss about scalability.