I don't think much about expiry dates (except involving fresh meat/fish), I think it's mostly a scam to make you throw stuff out and buy more. I asked my pharmacist once about taking out of date Paracetamol, and he said it "may" just affect the effectiveness, but it won't hurt you. I usually go by the one year rule with pills (after one year out of date they may not help anymore). (I wouldn't do this with liquid meds, though. Even I have to admit, they do lose potency more quickly.) I think you'd be fine to take vitamins. And "Best Before" means just that...not that they are "expired", just that they will be better if used before the date listed.