I just add distilled water to them when the humidity starts to drop in my humidor. I have the 65% beads and they hold the humidity (according to my hygrometer) between 64-66%. Once the humidity drops to about 61%, I add more water. Make sure you have a quality hygrometer and that you are not relying on the one built in to your humidor (unless you have calibrated it and are certain it is working correctly).

Mark