If the play (Credit spread) runs in on ya, you need a walk away point. Unfortunately that discretionary.
For some its +-30delts (individual stocks I loosely follow this depending on the charts)
Most others get a % away from ITM Say like 2% away from ITM they will close out that leg.
Sometimes if it runs the first week against me to say +-30 I'll close out S-Side. If its on the index(s) I generally dont close on the +-30 d's because I have the time and diversification working for me. Most of the time on index(s) If it runs closer to my play, I just legin the opposite side, Credit Spread to Iron Condor, and roll that new postition in as I make a decision (close for loss, close S-side only and let B-Side run) on the opposite first play.