There have been 3rd party tests on the shelf life of CBD oil, which basically involve putting the CBD oil through various stress situations (i.e heat and humidity) that they might endure in the real world. After putting the oil through the mock "real life environment" they would then test for peroxides, a chemical byproduct that is prevelent once the oils start to break down. After being tested month after month, the results showed that the CBD oil stayed consumable for over two years or just about 24 months. Even so, the oils were found to be harmless and edible even after the two year shelf life, it would just taste a bit off.
With that being said, CBD is a consistency game. The more consistently you take it, the better the results.