Also, I wouldn't expect absolutely rock-stable humidification with ANY system. I have the 70% beads, and I noticed that the humidity runs a little high after I moisten them, and a little low (even though many are still clear) when I need to moisten them.
Yet, it is the most fool-proof system I've seen.
Also, it seems the more beads you use, the greater stability you can achieve. You can't use too many.