Hcg should not lose potency for 60 days if stored correctly. Again it will only lose potency after 60 days not just go bad. As far as mixing goes if you mix it with 10 cc of bac water then 1 cc represents 500 iu after its reconstituted. If you are running it during pct it would be counterproductive as it will suppress lh as hcg mimics lh. I suggest running the hcg during the cycle when lh production is minimal right up to 3 days prior to starting pct.