We make cupcakes within 24 hours of consumption (meaning if we have an order for cupcakes that are to be picked up on Friday, we bake them Thursday night); they’re frosted/finished then refrigerated until the client picks them up or we deliver them. We have no control over when the client is serving the cupcakes, we can only go by when they want to pick them up. For an all butter cake or frosting, it needs to be eaten at rm temp so you aren’t eating cold butter, so we tell clients when they should take the cake/cupcake out of the fridge for best results.
So, what Julie said Take your cue from whichever is the most perishable thing. For the frosting, it means that after 3 days at room temp, you should be discarding it, not trying to buy another 3 weeks by THEN putting it in the fridge..
I wouldn’t necessarily keep this (or anything else) out at rm temp for the maximum allowable time recommended. If we have buttercream left at the end of the day, we keep it out til the morning; but if it is Saturday and we’re not in til Monday, it goes in the cooler. That whimsical buttercream stays soft, even when refrigerated so it would go in the cooler. I’d keep the frosted cupcake in the cooler because it will “keep” longer if it is covered and stored in the refrigerator than at rm temp. Room temp is different depending on where you are, but generally I take it to mean between 65-70 degrees F. If it’s summer and hot, that changes things. If it’s winter and cold, that’s another consideration. For example, in my area, I can leave a covered bowl of ganache on the table in the winter for 2 days with no problems. But I would only leave it out for half a day in the summer.