If you buy these ETH in the August, I think this is the good time to sell them. The price is $454 now. You can earn a big profit
Whenever people ask me what is the best time to sell a coin, I give them the same answer. Sell your asset when you need to, otherwise it is best to hold any digital currency for as long as possible because all of them have potential of returning profits at some extent.
Ethereum is the best alternative coin. Now it would have been much better if it was Bitcoin but it can also give some profits. Rest is up to the holder.