DO NOT keep coins at Coinbase.
They have announced that they will not recognize coins from the hard fork to bigger blocks on Aug 1 (BitcoinCash). So if there is a chain split, you will only get coins from one fork and they will steal your coins on the other.
Why would you store coins in any online wallet permanently, even if they are the best wallet / exchange in the world they could still exit scam or "Get hacked" and then you can say goodbye to all of your coins
and in regards to the announcement of course they will only give you one fork, because if they gave you both it would lower their profits and as a greedy piece of scum that it is as a large company its main objective is profit.