It works well to store your coins on any exchange but if you plan to HODL for the long term or at least a while it is always best to move your coins into an external wallet where you can control the private keys. If Kucoin gets hacked you could lose your coins or if kucoin goes down for any reason you could lose your coins if they don't come back. Maybe it's a small risk but its a risk nonetheless. I typically only store small amounts of coins on any exchange that I can use for fast trades when prices dip and the rest gets sent to my personal wallet. I just wish there was an easier way to keep track of so many coins in a single wallet since its kind of a pain to manage 50 different wallets but maybe that's just me liking to diversify my portfolio.