It is impossible to predict anything regarding the increase/decrease, the occurrence of volatility is always mandatory and at any time. It's not like trading based on time zones/days or weeks. If you choose ETH and LTC, I would suggest holding them instead of trying to trade. They are the best coins, trading just makes you lose time and lose sleep because of that instead of thinking long term and trust
Actually if a trader can allot his time to trade every day, I think that would also not be wrong to do, because trading will also make everyone better at understanding the market situation, rather than just keeping it and waiting for the magic to come to the coin.