how long can buttercream icing stay out of the refrigerator?!
Answers:
no, butter cream does NOT need to be refrigerated.
i work at a bakery and we make ours from scratch and according to the food inspectors, sugar is a preservative, just like salt is and it creates an unfriendly environment for bacteria.
That goes for cream cheese frostings as well.
We only refrigerate the extra when we make a huge batch but a 5 gallon bucket stays out all the time till it is used up.
ditto cream cheese frosting and the others as well.
You cannot frost delicate cakes with stiff frosting.
If it's not too warm, and get eaten that day, you'll be ok. If it's too hot, the butter starts to melt and the icing gets grainy and starts to separate. It still tastes OK, but it looks funky.
3-4 days if covered.
Just cover your cupcakes, they'll be just fine.