I think everyday is a good day to buy BTC and ETH. Those coin is the best coin right now because of their price and both prices always increase. As you said, we have to buy or collect the coins for storage. We have to wait until the price goes up and then sell it. Make sure that we have a lot of advantages so we can get a lot of profit from there. The problem is, actually I do not know if the price of ETH will go up like BTC. I just dare to save BTC for a long time. But if I work and get paid using ETH, I might as well keep it, it's just that I will not be too hopeful of ETH because I know BTC is a top priority and will satisfy me with huge profits.