Whipped cream collapses within hours because it is made with air alone, but two stabilization methods can keep it thick for days, according to the source material. The first method uses gelatin, and the second—adapted from baker Nancy Silverton—uses sour cream or creme fraiche.
To stabilize whipped cream with gelatin, dissolve 1 teaspoon of gelatin in 2 tablespoons of boiling water. Cool the mixture to room temperature, then drizzle it into the whipping cream when the cream is halfway thickened. Continue whipping a little longer than usual, until the cream holds medium-firm peaks. 
The simpler method, which the source says has been used for several years and never fails, calls for beating 1 to 2 tablespoons of sour cream or creme fraiche into every cup of heavy cream. According to the source, this does not make the whipped cream notably tangy, but it keeps the cream stable. Jars of stabilized whipped cream stored in the refrigerator have remained just as fluffy as on the first day after 4 to 5 days, the source states.
Both methods address the same problem: whipped cream's short lifespan. The gelatin method requires more steps and precise timing, while the sour cream method is faster and requires only two ingredients. The source does not specify whether either method affects flavor beyond the noted lack of tanginess, and it does not provide storage temperatures or food-safety guidance.
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