If you wish to hold some coin then use exchange only for during exchange. Just exchange your coin and transfer on your personal wallet that you have controlled. Specially you can use hardware wallet.
Because many exchange hacked buy hacker. Many people loss their capital by hack.
So please don't hold your coin on exchange for long time.
We really cannot say that because some coins that if you hold for a ling time their price rise up and jf there are a new exchanger that comes usually the price is much higher than the previous one so that is much more profit. But of course there are some times that when you hold too much what will happen is the coins will die soon until it comes to the point that you cannot sell them anymore because they are really worthless. But again it depends on the coin