I think whenever the time is right to buy bitcoin because no one knows for future bitcoin prices will rise or fall. It depends on ourselves whether just to get a little profit or to profit a lot. Buy bitcoin and sell it when the price goes up may be very profitable if you wait and be patient in long-term trading. But if only to get a little profit can buy and sell anytime when he feels he has benefited.
Although the prices of Bitcoin are dropping so bad for so many times already but I strongly believe that this is the right time to buy while the market price is too weak so we can buy more bitcoin that we can hold for long term investment.