It is generally a good idea to stow your cigars after you first get them in an environment that is 70%+ RH and let them sit for a week or two. If your cigars are in a dry environment, the wrapper is obviously the first thing to suffer. By extension, it does not take much to dry out the wrapper. I have taken perfectly humidified sticks out with me when fishing or hiking in the winter and the wrappers dry out and crack within just aa couple of hours of leaving the humidor.
So the advice is to give your cigars a good long rest when you get them to let the humidity equalize, and make sure that they stay at +/- 70% as best you can.