Yes, you should stop buying it with the present price, it's 8k3$ and it already cross the target for buying. If Bitcoin back to 7k$ i will spend all my capital to buy bitcoins.
Stop when you do not want to make money, actually that depend on your purpose, if you want a long term hold then anytime you can buy bittcoins at any price. It's only traders who needs a good timing in buying so they can benefit selling it in a short period of time, right now bitcoin is on pump and they are waiting for a bad news that will create FUD so the price will dump, when the situation will happen, they'll accumulate as many as they can and then sell when the price back to normal.