Do beads go bad?

I suspect your sealing.
If your seals were tight then the only reason to add water is for you opening the humi. A tight wooden humidor will lose moisture slowly through the wood but with enough beads that will not effect the humidity until the beads are almost spent. Then it would recover quickly with a little moisturizing. At least that is my experience. I have a couple of airtight cedar lined ammo can-a-dors that I keep humidified with Bovida pouches. I am rarely in them and they stay perfect.