HCG is sold in the pharmacy with an expiration of 2 years. So you wouldn't be able to "sell" it after that time frame. It is good for years. I have seen studies whereas hcg was 99.9% purity after 10+ years, when stored properly at room temp.
HCG when mixed, the old "bro science" is that it is only good for 30 days. How that became established is bc studies, once again, prove that BAC water is only sterile for approx 28 days. After those 28 days, fridge or not, it is likely that it is no longer "sterile". That doesn't mean it isnt potent or usable, it means that you should not be shooting it IM after that time frame. You want to use it subQ if it is "expired". The risk of any type of infection is very low and the really only side I have seen in users using very old hcg that has been expired for awhile, is a rash at the site of injection or lumps/welts. In terms of potency mixed HCG is actually close to full strength if not full strength for many months. It gradually loses potency once mixed.
I have used hcg that is a year old before (mixed) and it still worked and was very potent.
Powders would likely be several years at least. 15 years ago the inserts siad HCG was good for 90 days after reconstituting. Seems that has changed to 30 days at most for most all injectables. So i tend to think well over 30 days is fine.