Coins should always be considered in a safe storage, there are lot of wallets and platform that could be used to hold coins, both of this has good side and bad. Where will you choose to store or hold your coins, in a close source wallet (exchanges) or an open source wallet like electrum and Hodler wallet?
Definitely it is not going to be exchanges because you can see that many exchanges where hack in the recent times. Better to store your bitcoins in the wallet where you have the private case like electrum if you are holding high amount of bitcoins then you should probably buy a hardware wallet.