Probably should have posted this sooner but better late than never.
Enough humidity is as important to your board as to much humidity is not so good for your board.
A couple of years ago I made a 18″ x 20″ x 2″ cherry board for my wife which stays on the kitchen counter. Once winter and the dry air that comes with it rolled in, the board which was flat bowed in the middle and rocked. Fortunately all we had to do was turn it over and the rocking was gone but there was a hump in the middle. We used it anyway and once the warmer more humid air of mid – late spring arrived, the board returned to its normal flat state.
Using a decent thermometer/hygrometer that I picked up at Amazon I found that just relying on the humidifier attached to the furnace the humidity in the house was only about 20%, which is way to low not only for an end grain cutting board but any wood items in your home. I recommend any whole house type humidifier but personally like the one with removable water jugs that you fill and replace. I’ve been keeping the house right around 43% humidity and none of the boards are bending or bowing. Also, the oak floors in the house are appreciating the extra moisture as well. I’m not seeing any of the gaps between the boards that we have seen in previous winters.
Don’t forget to condition your board each month!