This frosting lasts up to 4-5 days stored in an airtight container in the fridge in an airtight container. While it does well at room temperature due to the gelatin, it's still a dairy-based frosting and so is not ideal for high heat for long periods of time (such as outdoor parties in the summer!). I recommend keeping it chilled. At room temperature (below 75F/24C) I wouldn't leave it out for more than an hour or two.