It depends on the goal. For the long term investment, I prefer to hold established altcoins because it will be quite safe to a long time. Moreover, if the altcoins have been proven to always continue the development. It is a good reason to hold the altcoins for a long time. But if the altcoins have bad issues, I recommend to avoid holding for a long time. It is too risky if the altcoins can be delisted from the exchanges. However, for a short term holding, it is no problem to buy new altcoins. But make sure they are potential altcoins, we don't buy random new altcoins!