When the price Hits bottom around $4000$-5000$ or even lower start buying and do not buy in one go make your purchase spread over a period of 4-6 months. And then Keep buying till 2020. Yes right don't plan on selling before 2020 buy as much as you can as cheap as you can. But don't sell before 2020.

I agree with you Dear @rzs

Thanks @maujmasti