[shilala]

I use an Avallo and tons of beads in my big cabinet humi.
The active humidification maintains the beads, and the beads take up when the kids pull the extension cord out of the wall. It works great, the set point never budges, and I've put water in the Accumonitor exactly twice in two years (my cabinet is not remotely as well sealed as one of Bob's humidors). I have the smallest one, forget what it's called. The mini or something, it was around 200 bucks, iirc.

I like the active/passive combo because it completely does away with humidity spikes and keeps a rock-solid RH with as close to zero maintenance as it gets.
Whether it's overkill or not is a matter of opinion. I've got about 500 bucks worth of humidity control apparatus caring for many, many thousands of dollars worth of cigars, and it's flawless and secure. The setup is worth it's weight in gold to me.

For what it's worth, the active/passive combination idea certainly wasn't mine. I picked it up in my reading back at Club Stogie. I also thought that if things were sealed up real tight that the RH would run away on me, just by virtue of the Hydra being full of water and more or less open to the environment inside the humidor. I figured it'd create a "saturated beads" situation like the guys have mentioned here. I was never able to produce results like that, and still haven't. Nor have I ever heard of it happening to anyone.
If a humidor was sealed tight enough and seldom (or never) got opened, I can see it happening in my mind's eye. I even ran a Hydra with beads in a desktop and wasn't able to make the RH run away on me.

What I can mention from those trials is that the little Hydras are far less accurate and sensitive than the little Avallo. The Avallo has held up flawlessly while the Hydras broke left and right, making it a far better value.
I've heard nothing but good about Bob's set and forget, I don't think you could go wrong there. Some are nearly identical to my Avallo, I'm sure I'd be happy with them, but I do believe Avallo's might be a bit less expensive.