From Longman Dictionary of Contemporary Englishfor keepsfor keepsinformalALWAYS/EVERY TIME forever Marriage ought to be for keeps. → keep
Examples from the Corpus
for keeps• Marriage ought to be for keeps.• I'd threatened to leave many times before but I believed in marriage being for keeps and trying to make it work.• Marriage is for keeps, we say.• He's given it to me for keeps.• They lead with their hearts and they play for keeps. 