Be careful if you choose a long-term investment with the altcoin because you need to choose the right altcoin to buy so you can make a big profit in the future. Right now, there are too many altcoins that could be potential to rise in the future, and if you can buy at the low price, you will get much amount of the altcoin, and you can make a big profit too.
It is already a given that when you decide to invest on something, you should know already what kind of investment is that because if there are some events that may affect the price of that altcoin then you can act fast. If you want to invest in a coin for the long term, it would be a good idea to take profit from time to time so that when the market is not doing good then you can adjust your holdings by either accumulating more if you have extra funds or selling it earlier and maybe incur a little loss and then buy back later on when it has a cheaper price.
Investing in a coin for the long term is too risky for me because coins are unpredictable and price is very volatile that's why as much as possible when you have the chance to take profit then you should grab it.