How does the HCM work in reducing humidity? My ambient RH is always higher than 65% so I only need them to lower and probably never needs recharging.
If your humidor seals well then the HCM beads will do a great job of maintaining the RH inside your humidor.
If your humidor does not seal well, then the beads will do a great job of reducing the RH in youyr humidor, until they absorb enough moisture that you need to dry them out (there are instructions included with the beads and on my website that explain how to do this). A higher ambient RH means that you need to use a refrigerator to dry out the beads rather than just leaving them out.
You can see from the picture below that each bead is like a little sponge that is precharged to 65% of its capacity to hold moisture. These beads are designed to maintain an equilibrium in a closed environment. If the RH is low the beads will release moisture; if it is high the beads will absorb moisture.
I go through this all the time. One of my humidors seals great and I don't have to think about it. My other humidor does not seal well and my ambient RH is low (30's-40's right now), so I need to recharge the two 8 ounce bags I have in there about once a month. I have tried fixing the seal, but have not had success at this. I takes about 48 hours for me to bring my beads up from 62% to about 68%. (I like my humidor to be at 65%; I bring the beads up a little higher to help them overcome the poor seal.
I am not trying to turn this in to a sales pitch and I apologize if this post comes across that way; just trying to answer the question that was posed.