I've popped open all of my old floral foam humidifiers and replaced the foam with the kitty litter crystals. It's easy enough to tape them back closed with a little clear packing tape. In my bigger humidors, I've also used plastic dishes filled with the KL and just set them into open areas. I replace the KL twice a year or so or when they start to yellow and it's worked great. Consistently between 65% and 70%--and only 70% during the first week after refilling since I tend to soak the KL in the dishes well with distilled water, until there is a little water sitting at the very bottom of the dish. On rare occasions this has caused a reading above 70% temporarily, but I just open the lid and pull the trays for a few minutes and then close everything back up and that seems to fix it.
I can usually go up to 2 months or so between messing with the KL without any problems. Waiting this long actually brings it down to 65% for the majority of the 2 months and I have over ten humidors (no towers or coolidors), so it's worth it for the time I save dealing with refilling. Takes me 2 hours to rehydrate everything each time, so only messing with it 6 times a year is preferable. I think next year I'm calling on my friend's friend that makes custom cabinets and going professional with my setup.
