I am making a cake for my husband's birthday next weekend and was wondering how far in advance I could make the icing. It's an icing mix from GFS, all you do is add water. Has anyone ever used one of these? Do you think I could make it in advance or should I just wait until I'm ready to use it? Thanks for all your help...I'm very new to the cake world!

I have never used this kind, but maybe this will bump you up and someone will respond who has used it. Sorry.