When I took classes - I was told it would keep unfridged in an airtight container, out of the heat and sun for 2 weeks. There was a post on this subject a while back and some people said that they actually froze it for months and then let it thaw and re-whipped it and it worked fine. Well, I tried it and it worked! That's what I do now if I have left-over that I'm not going to use in a short period of time. The other option is to do some quick "drop-flowers" - let them dry and put them in an air-tight container so you'll have some ready made flowers for those "sudden cakes needed".