Altcoins with real use case will never disappoint you on the long run ,altcoins like clear foundation ,Hot (hologen) and skycoin will never disappoint because they have a real use case ,if you choose wisely you Wont have anything to worry about.
There are some altcoins that are BIG if you know how to pick them out ,some are backed by popular bigger companies like Microsoft among others.
Do not choose coins because they are mineable or they have implemented POS ,without real use case they will die overtime and lose value.
Holo (HOT) is one of the best coins to hold on long term. Have large transactions and traded at binance. Its true that we have to choose wisely if we are going to invest in altcoin because the risk of investing in altcoin is very high and sometimes there are many altcoins that only pump and dump projects