A: Depends on the quantity of cigars stored, the size of the humidor, and the climate in which the humidor is placed. That said, as a general rule thumb check up on it every 2 weeks, if you shake it and it rattles (because the crystals are dry) you need to refill. I'd say you can easily get 15-20 fills out of it. I personally have had one for 2 years and it's still going strong. Hope this is helpful!
A: You should be good either way. Once the crystals fully absorb the distilled water they turn into a jello like substance and the moisture only evaporates but never leaks. I've had the most success hanging the device towards the top of my humidor because moisture falls.
A: The HX10 works ideally in medium sized humidors ranging from 75 to 125 count. If you have a larger unit, you can always use more than one. However, I would not suggest using on smaller humidors, as you will probably over humidify your collection.