What you must know with altcoins is that once the price is dumped it becomes almost impossible for it to recover and that is why altcoins are referred to as gambling, you can't rely on them and as a matter of fact, investing in altcoins should be done with a predetermined mindset that anything can happen and the investment could visibly become zero.
This is why altcoins are not suitable for long-term purposes because their markets are highly unpredictable and for sure not suitable for long-term holding.
Actually not all altcoins are not suitable but indeed for the long term the risk is big,
for long term stay top coin is still a viable and safer option,
The most important thing is to always do your research before investing.