My advice to engineer is always:

Your job is to make sure that the decision makers, when they're not you, have the information needed to make competent decisions. You should keep arguing when (a) there is credible reason to believe that important information has not been heard or understood or (b) when new information has come to light that you credibly believe might change the decision. In the absence of those two, your should accept that you have done your job and should let your managers to theirs, even if you disagree with them. Bring it back up when (a) or (b) changes, and not until.