I don't know about other cooking oils, but I do know that camellia oil is the most heat-resistant cooking oil, so if you store it indoors in the absence of sunlight, it will have a shelf life of at least 2 years.

As for the 18-month shelf life on the cooking oil packaging, that is the maximum shelf life of food products stipulated by the state, which must be labeled as such, there is no way.

You mentioned that the older the tea tree oil, the better, is not quite right. The countryside of the earth pressed tea oil are not filtering procedures, so there are many impurities, stored for a long time, these impurities on the precipitation, the oil becomes bright, and the quality has not changed, so there is a tea oil the older the better rumors.