You are right, it preferable to go for a longtime investment because some coin aren't strong enough and beside there is alot of altcoins that are intended to pump and dump so will all need to be careful and research a lot about the coin we are going to invest to.
This is what I've learned in investing for years that anything could happen anytime in the market so we have to be skeptical in picking a potential coin to invest with. During the dip, most coins could drop their price but not all of them could still recover so we have to be wise and mindful in choosing a coin. We should always check on their capability and history.