I bought when price of bitcoin went down to $900 in past few weeks and that was a good move as now price is at $1300 so I have already made some good profits from it but I will prefer to hold them for even some more time.
I also buy bitcoins at a time when the price goes down. After every bad news, prices usually fall and all newcomers panic.
Now I can sell bitcoins at a high price and I will have a profit