When you refrigerate teeth whitening gel it will keep longer than when it's left out of the refrigerator.
When you refrigerate teeth whitening gel it will extend it's shelf life to 2 years but when you leave teeth whitening gel out of the refrigerator it will last for only 1 year.
You can still use expired teeth whitening gel but it loses it's effectiveness once it gets past 2 years old so it's best to use the teeth whitening gel within 1 to 2 years for best results.
Using fresh teeth whitening gel will work the best to get your teeth white but as long as you refrigerate the teeth whitening gel it will still be able to whiten your teeth for up to 2 years.