I think you should always cash out your money every time btc is pumping, for example last december btc reach 19k$. I cash out a lot of money.
There is no definite guide about when we can cash out. Actually as long as it earns profit, then it's okay to cash it out. I don't think it's necessary as long as we don't take any loss. The matter is in how much we got in the profit and how greedy we are in getting profit. There is always a chance to double the profit in next times.