It really depends on the altcoin and the market. I have made several long term altcoin investments that have gone nowhere but are poised to go up in the future. It's easy to lose money right now so maybe stick to erc tokens or some shit
Investing in altcoins depend on the market. It is good when it become successful during its ICO because many investors want it that can result to have a high price and get huge profit if hold it some time. Some altcoins do not give profit even you hold it long time especially if not really become success. Even it is introduced in the market, the price will still low and having small number of investors