You’ll know when essential oils have gone bad, because they will begin to emit an unpleasant, rancid odor, and will turn murky or cloudy.

Exposure to sunlight, the air, and high temperatures can affect the quality of essential oils. So, when you buy essential oils, they should be in an amber glass bottle, and preferably have a very tight lid. They should also be kept in a cool place.

The strength of the scent is affected.
Yours are probably in Dark bottles also.

Open the bottle and the strength of the fragrance will tell you right away.

Properly stored, who knows. We have used patchouli oil, I think dated to the 60’s , LOL.