Jell-O stays fresh for seven to 10 days in the refrigerator once it has been mixed. Vodka, which is often used to make Jell-O shots, stays fresh for an indefinite amount of time if unopened.
If the Jell-O shots change color or develop an odor, this may be a sign that the vodka in the shots is no longer fresh. If the Jell-O develops a bitter flavor and water starts to collect on the sides of the Jell-O, this means it is going bad and should be discarded. It is best to prepare and eat Jell-O by the "sell by" date on the package to ensure the food is safe.