question on 12/12

hey guys i want to thank you all on the amount of knowledge here, and have posted a few times, but read your guys great work for hours, i tried searching but forgive me if im wrong and there was a post, but im putting my plants thru there flower cycle, and doing 12/12 do they have be doing 12/12 consistently, like 9-9 everyday or does it matter, or will ti turn back to veg mode if its not consistent? thanx
 
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