A lot of exchanges are the main target for crypto-hackers. Remember that : if you keeping cryptocurrency in the exchanges wallet they are not 100 % safe.
The best way to store / hold currencies in the long time term is to hold them offline for that you can use paper storage or ledger storage. I know there was a lot of articles on that subject but i can see that a lot of people's still don't know that!!!
Dont be stupid just buy and hold safe you money. You dont need to curry the risk with others. When you got it offline you can be sure of that your money is 100% safe.
The best crypto-traders keeping only 1% - 10% of their porfolio on the exchanges. Remember that!:)
Enjoy