An unopened box of JELL-O mix does not have an expiration date. and can be safety stored in the pantry for 3 to 4 months, according to Eat By Date. This time frame applies to both unflavored and flavored varieties.
Unopened containers can be stored in the refrigerator for 12 to 18 months past the printed dates.
Pre-made JELL-O that has been opened should not be kept in the refrigerator for more than 7 to 10 days. Opened dry mixes can be stored in the pantry for 3 to 4 months.
If Jell-O becomes watery and begins to separate, it should be discarded because this can be a sign that it has spoiled.