That varies. I don’t think it’s so much an issue with right and wrong answers as the “automated trailing stop question” is.
The simple, short answer is that you exit whenever your thoroughly tested, proven trading plan tells you to exit.
For example, if you’re in s short trade because your chart analysis has suggested that the price should start moving down pretty quickly from where it is now, then a valid reason for closing that position early would be simple “the failure of that to happen”.
If your trading plan doesn’t tell you when to get out, then you need to do further work on it, but the exit has to fit in with the reason for opening the position.
Two things which I think may help you quite a bit are (first and foremost) a book called “It’s when you sell that counts” by Donald Cassidy; and (secondly) this page : -
Other examples of “when to close positions” could include ATR fractions or multiples, according to timeframes, areas of congestion, next support/resistance levels, round “psychological” numbers, and so on.
Having a too-high reward-to-risk ratio can be a kind decision-delaying mechanism, the way some people use them. Just something else to be aware of. But it’s certainly fair to say that this question, in my opinion, is one of the more difficult ones in trading, and perhaps one with one of the widest possible ranges of answers.