Bitcoin is a long term investment and never expect that it will make you rich overnight so if you have patience to hold your bitcoins for a long term then any price and any time is the best to invest in bitcoins as in long term you will only get best and positive results on your investments.
I agree with that there's no such time is right to invest with bitcoin because every time is the right time as long as you go for the long term investment because bitcoin is the best for it because as you can see bitcoin price is growing every year as you can see the chart so maybe by holding it for a years you will have a huge earnings because the bitcoin is good for long term investment.
Not only for the long term, it's easy to earn with small term holding too if the price move happens same as now with certain time interval. Investing gives the profit to the users, as it is growing as well fluctuations were happening which tends to move forward even if experience a fall in price.