Expiration on Evening Primrose Capsules?

Zoe • Vegas Mama

My bottle’s label has been worn down but I know bought it December 2017. When do they normally expire? I read that they never truly expire they just lose potency and I don’t want that either so I was wondering if anyone has a bottle and can give me a time span when their’s says it’ll lose potency/expire. (For example if you bought the bottle Jan 2019 and it says expired June 2023 then the time span would be 4yr6m)