I bought a bunch BTC when it was $17000, then bought a bunch when it is $14000...then the price dropped until 2 days ago. I bought a bunch again when it was 6000ish...haha, now the price went up...so, really, when is it a good time to buy? When it dropped for a while and it rose a little bit, then drop again, then buy?
Now is a good period as it will soon reach about 15k so it's at the lower limit which points out that reasonable investments will be useful now. Don't wait for when it crosses the 12-15k mark as prices will remain much more stable at this points which will lead to reduced profits in the long run.