Of course, you can keep your coins / tokens for many years. But here we should look at the risks. For example, the dev will drop the altcoin or switch to the new altcoin and you will have to exchange your old altcoin for the new one or you will lose all your old altcoin. But if you want to trade, you should monitor the market price well by doing a very good research on the project, and make sure the value goes high before you sell it.  You can also buy many different tokens. If one of them works at a very high price, you win!