I do say this to people but I don't think we should always stick to them.

If you really are taking care of your balance, you should really stick to them but you should have the knowledge of investing and trading them since they are popular, the volatility is much higher than those lower altcoins. Since you are already taking a risk just by investing in cryptocurrencies, take a step further by investing in some good altcoin. As I always said, gain knowledge since that will really help you become a successful trader or investor.