I wouldn't freeze the sauce because it won't defrost well - melted butter doesn't act the same as non-melted butter in this way - because melting it essentially separates the solids from the liquid, when you freeze it it will turn out a little grainy in texture which you don't want. You can refrigerate the sauce thought for up to 1 week and use it in lots of ways, so don't be worried about having too much leftover.