Altcoins can also be purchased and held indefinitely but not all alternative cryptocurency because many of them aren't worth it because of their poor design and only increasing in price because of their community hyping them. some altcoins has been in the market close to when Bitcoin started becoming very popular. Altcoins like Dogecoin has been in the market very long.
Altcoins like Ethereum has also been in the market very long and some of the new altcoins that has been created will also last for a very long time. BNB will be one of the coins because the CEO is working very hard to make the project one of the best in the industry. Altcoins has more potential than bitcoin because altcoins can increase more than Bitcoin in bull market.
We have many altcoins that are currently trading and popular that are bad but we have some good ones that can be profitable and can make you rich in a very short time therefore we shouldn't call every altcoins in the market bad for investments, what we have to do is to filter the market and select the good ones and invest, both altcoins and Bitcoin can make us profits.