Keto diet - length of time

I am considering a temporary keto diet. Temporary because I am not sure how long I can last with no carb (lol). 

Is this still effective if it is cycled on and off? Does anyone know the minimum amount of time I'd need to be on this for it to make a difference? I was thinking a month on and off. Would love to hear I could do it weekly but that seems wrong.

Thank you in advance.