There is no guarantee, lol. I use them too sometimes, and they are really nice. But the Boveda's can only do so much. If you jar them too moist even with the pack you will have problems. They are better at raising the RH in the jar than lowering it. I always have some ready though when I'm getting close to harvest time, along with extra mason jars, lol. I've got more jars now than I originally planned on having when I started, and I still have to keep buying more, hahaha. Just got 3 more cases a few days ago.