As we all know exchanges can get hacked, caн be down for a long time, can held transactions and so on, so obviously it is not a good idea to keep your coins in them at all times. But then comes the transaction prices, if we move the coins always, we pay extra for the transactions we make. Perhaps the decentralized exchanges where you can directly log in with your wallet will help solve this, as you have the control over your wallet and not the exchanges.
I'm not going to recommend to you guys to use exchanges as a storing place to your coins even though it is a decentralized one. I suggest you guys to use a wallet for that, it is important that you have the control for all of your coins, and having your own wallet is a lot of reassuring than storing it on exchanges. Also having that fact that an exchanges could be down for a while and that would be annoying if you really need to sell some of your coins for fiat.