I don't practice holding coin in exchange for a long time. Because some exchange was hacked and many coin are stolen. So i am afraid it would happen to me if i hold my coin in an exchange for a long time.
Here, I dont think the problem is in bitcoin or their holding, despite the fact of such untrust worthiness, I still suggest you to take better information beforehand. You must know each and every detail about exchange through witch you are going to make trading. Only then you go and make some money and you can hold for long time and you May Day trade there.