I personally think it is a good idea, but you also need to be aware that in this altcoin economy everything it is possible and it would not be so unlikely to see an eventual drop in the bitcoin price, however most analyst are totally convinced that the price of bitcoin is undervalued and sooner rather than later it will hit the barrier of $1000 again, so it is undoubtedly a good long term investment.
That's why it is a good investment when you see Bitcoin drop (That is when you buy it). Also cheap prices means higher profit its a simple way on how to get money early on to your investment however timing it will be a crucial step as we don't know how the price will drop or if it drop to the lowest it can until it bounce back up. So we must really study Technical Analysis.