The problem is sometimes whales take action suddenly and chances are we also don't know what whales will do later, although it would be better to trade by following a step whales, but I think whales is currently not visible, even what appears in crypto is small fluctuations and there is no pump or a large dump.
Whales might be tired after dragging bitcoins from $6500 to $3500 in less than a week time 
. But, I am not sure how easier to follow whales even some telegram and skype groups are claiming that they are having access to whale's order-books. I never believe into such a bump and dump groups.If market is bearish then you can buy many coins at lower rate and once it begins to rise it will be quick and fast growth so you can make more money in less time . On other hand during the bull run if it starts falling then you are struck .
Buying in falling markets and then waiting for long period will enable anyone to crack profits regardless of when bulls may fail or when bear will come to action. Simply plan for long duration then you get avoid getting struck. I agree buying at the end of downfall may give me quick and big profits but you cannot buy at exact bottom also so you cannot be sure about continuation of bulls after you bought.