I think there was a thread on here a while back that pretty much said you're good to go for at least 6 - 12 months after the exp date. And even at a year you'd looking at minor losses in potency. If you don't believe me, use the prop you have after the exp date (short acting ester, you'll be able to tell soon whether or not it's working). I used a bottle of tren ace 100 mm/ml 6 months after the exp date and within a week my strength and aggression were way up as usual. And also remember, some of the more reputable labs OVERDOSE their preps so even a year after the exp date it might be back down to the dose that's actually printed on the label.