In my wash stand humidor, the humidity is stabilized by lots of unfinished wood, a small, "granule" humidification canister, and an always open, 14 oz. bag of the world's cheapest black Cavendish pipe tobacco.
The latter is awful stuff to smoke. I never smoke it. It just sits there wide open, absorbing excess moisture, releasing moisture when needed, and giving the humidor the aroma of a tobacconist shop.
The bottom line is humidity ballast: wood, bag of crappy tobacco, humidification granules, and all the cigars and leaf contained within.
Naked cigars that are exposed to rapid shifts in humidity exhibit changes at the open end (foot) first. So the foot can split if the filler absorbs moisture faster than the wrapper, or if the wrapper dries faster than the filler. Cigars in cello are slower to react to changes in the humidor's humidity.
Temp changes within the humidor work their evil through their effect on the humidity. If the temp increases by 20ºF, the RH will drop by about half. Pretty severe.
So, my indoor humidor that is kept in a reasonably comfortable temperature zone, and contains lots of humidity ballast, its roomy interior seldom changes its RH by more than about 1% per week.
Bob