Here's another reason not to wait till expiry:
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OTM options will have a swift drop and then the curve bends back. You got lucky that the drop occurred real fast in your trade but you are basically standing at the midpoint and the theta decay will be slower and slower. In the mean time you remain open to market risk. My rule of thumb is to close such long term credit trades when I get to 2/3 of the theoretical profit. (Yes I have sinned many times against this rule! Dont do as I do, do as I say.)
Thanks for this info. People usually advise to close options positions at 50%. Just that this magic percentage is a mystery to me. The underlying can go in your favor weeks before expiration and you can close out at 50%. Or it can hang out near the strike days or even hours before expiration with 50%.