As previously mentioned, you can recharge them. Something to keep in mind when recharging them is that it is possible to overcharge them. Being a salt solution, it doesn't actually hurt them, they just cease to regulate at the advertised humidity levels and will run high RH until they've given off enough water to drop back to the proper water : salt ratio. According to the manufacturer, the small packs are 8 gram and the larger packs are 60 gram. I've tested these elsewhere and found that you can go about 20-30% over and still hit target RH. Additionally, you absolutely can submerge the packs in water to recharge them, although with the white packs the outer label will tend to fall off (brown packs didn't seem to suffer this problem), aside from that, it's fine. The salt solution can't pass through the membrane because the molecular size is too large, by this same token, only water is going in, so, in theory, you don't even have to use distilled water because all the other crap in the water has a larger molecular size, although, if you use the submersion recharge method, bear in mind that "the other stuff" can be deposited on the outside of the pack. I have found no limit to the number of times the pack can be recharged as the salt has no way of getting out.
