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.
After the continuous and unexpected surprises that the price of bitcoin gives us frequently, I have learned that I should not be overconfident when deciding what to do with my bitcoin holdings, since it has been demonstrated that in the path that will take the bitcoin price to be worth a million dollars, there will be endless pumps/dumps and corrections that will make it especially beneficial to trade with our bitcoins, or at least schedule eventual cash outs. In my case I am exchanging some portion of my bitcoins for fiat after a very sharp rise to wait for a big correction and buy back.