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.
Probably its a great advice. Its better to be safe than losing your money. We have to be more secure if we can save in our personal wallet.