Stabilize it with a smidge of gelatin and it'll keep fine. Without that, it'll get weepy.
I don't recall the exact ratio, but it basically involves dissolving some gelatin in liquid (cream or water). Let it sit for about 5 minutes until it's dissolved into a gel. Make your whipped cream frosting like usual, then beat the gelatin in. It'll hold it's shape much better, but doesn't change the flavor or texture noticeably. Google for exact recipes. I think I used about 1/2 packet of gelatin with 1/2 cup or so of liquid for a standard batch of frosting, but it was a while ago and my memory isn't that good

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