I can't say enough about the kitty litter. I opened one of my humidors for the first time in 3-4 months since seasoning it and adding the cigars. I'd actually forgotten where I'd put this humidor. In it, I'm using a coffin case with KL. I opened it up, expecting the digital hygrometer to read in the 40-50% range. To my amazement, the hygrometer said 67% after three months of inattention. The humidor is one of those cheap Thompson Cherrywood 50-ct humis you get with their $30 sampler deal, so it ain't nothing special.
The other three desktop humidors I've got running on KL have similar results. I just popped open the plastic humidifiers, pulled out the foam, filled them with KL, stretched a piece of pantyhose over it and snapped the cover back in place. They have required less maintenance than the humidors I have beads in. I'm using the cheap Makall Mimi Litter I found at WalMart. I think I paid $2.99 for a 4lb bag.