Seasonal moisture gradients inevitably lead a small change in wood volume. Of course, these changes does not matter for cutting boards, nevertheless we have to consider it in practical use of the board.
In wintertime, house heating is reason of moisture decrease, and wood dry out; in summertime, moisture is increasing and wood is splaying out. In addition, it is clear you should not keep boards within easy reach of heating appliance. The only way to protect wood of moisture gradients is covering with slushing oil. In cutting boards case it is necessary to quite often (preferably not less than once a month) smear with mineral oil board surface to fill wood pores. With proper care, board will serve you at least 10 years.