Is it once you make a certain % profit? Or is it if you need the money? How do you feel about the fees? So on.
It depends on your greediness,in my average daily trades i can make 10-15% of my portfolio that gives me 300-450% per month,so if i achieve 10% in every trade i would be happy,cashing out when you need a money is good,but spending money in your needs would be much better.