When you have made money from investing in altcoins, you may keep at your wallet or at exchange agent.This decision depends on you. If you want to hold it within several months to come, it will be better and safer to keep it at your wallet.you have full controll on it and at any time you can cash or transfer to another. While keeping at exchanger, will be more risky because you can not controll it directly. This is my short idea and advice.