Keepin your coin on the exchanges is a really bad behavior, it is not recommended. You should put your coin in your own wallet, instead of keeping it on the exchanges. The problem of storing coins on exchanges is we don't own the private keys of the coins, because of that we can safely say we don't really own the coin.
totally agree with you especially since there have been a lot of incidents involving exchanges. What's worse is that you aren't insured at all.. So, better to keep your holdings in your wallet instead.