How to choose the number: look at how long your winners take to reach target. If most get there within 10 minutes, and trades lasting longer have a much lower win rate and often drift to the stop, a limit just above that, such as 12 minutes, makes sense. Your own duration distribution should set it, not a number from a forum.
How to evaluate it before using it live, from past trades:
- Find trades still open at the time limit.
- Score them at the price at that minute instead of their actual exit.
- Compare that total with what they actually made.
The risk is cutting trades that would have worked later. Check a sample of them. A few will reach the target after 20 or 30 minutes; the question is whether enough do to change the picture.
Does anyone use time stops on scalps? What time limit works for your trades?