I say ditch it. Unless your luteal phase is under 10 days then it's not considered an issue therefore does not need to be fixed. Vitex is also linked with early miscarriage - search engine it & you'll find loads of ladies who've had early losses whilst on it.... I had two... don't know if that's what caused mine of course but the very next pregnancy was a sticky one just 2 months after ditching Vitex. I was on it for mood swings, not for anything to do with LP.

Forgot to say I had a shortish LP - between 11-13 days but still managed to conceive 3 times within a 12 month period.