Winter Humidor Humidity?

[Heliofire]

So as winter temps and humidity begin to set it now I am noticing that my heartfelt beads are in need of more water more often than I remember they needed last winter. We keep the house around 70 degrees but I have noticed that the room humidity is around 35% so I guess that might make the beads dry faster and keep them a couple points below where I am used to seeing the humidity in my cabinet. I just checked the accuracy of both hygrometers that I keep in there (which i do every six months) and they are both still spot on. So I am wondering how many other brothers out there have had to do more work on their humidity in the winter time. As far as I know the humidity beads don't go bad right? If they do how long do they usually last before they need to be replaced? Thanks for any help or stories you guys might have on battling the dry winter humidity.