Not all currencies have long-term value. At the moment, new altcoins are constantly emerging and vanishing, most of them are empty with a white paper, without real value, or without a strong #DevelopmentTeam . Therefore, the short-lived altcoins abound. Worse, the altcoin you invest in may be a scam! Therefore, before choosing to invest in any cryptocurrency for a long time, you must first determine whether the altcoin has potential. I still do not recommend long-term investment in an altcoin unless you have faith to the fullest. This risk is relatively large and the return is small. A portfolio is a good choice. If you want to invest in a cryptocurrency for a long time, please choose a cryptocurrency with a strong popularity, such as Bitcoin, Ethereum. Although the prices of these coins are relatively volatile.
Btc price dropped dramatically since at the end of 2017.
Eth market meets bearish sentiment in this several months. But for long-term periods, there is a lot of room for growth in the future. So long-term investment in these big currencies is a good choice. Of course, if you are really optimistic about an altcoin, you can, of course, buy it after a hard job of research. However, it is not recommended to hold an altcoin for a long term.