the best time ? ithink it will be delayed this time just wait till the bitcoin price really small like $600 then invest all your money in bitcoin im pretty sure that you could get a multiple of earnings after a years all you need is patience and you need guts in order to take the risk. bitcoin is not that risky because while waiting till the bitcoin price increase you could play some gambling or maybe do trading addition in your earning.
but to me i think if you want to wait or this price, i think then you can only wait and the price of bitcoin is not coming down to this price, i think it is still better to trade bitcoin in the present price as you will never find any opportunity to trade bitcoin even in this price in future.
If you are going to hold your bitcoins for long term then I think even the current price is the best price to invest in bitcoins as everyone is hoping to see the price of 2000 usd by the end of the year so if you buy now then you can make good profits by selling them at that price.