Whipped cream is best served fresh, otherwise it will turn into a melted mess. But if you need to pre-whip cream, add a dollop of sour cream to keep the structure intact long enough to serve.
Anna Stockwell, writing at Epicurious, put this trick to the test. She explains that the sour cream didn’t affect the taste much, but the additional fat helps stabilise the whipped cream and insulate the air that keeps it fluffy. If you don’t have sour cream on hand, you can use greek yogurt instead. Adding one of these to your next batch of homemade whipped cream (plus freezing it for an hour) will make it last for two or three hours.
How to Make Whipped Cream Ahead of Time [Epicurious]